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Home / DTC / P1301 — Cylinder 1 Misfire

P1301 — Cylinder 1 Misfire

Detailed page for trouble code P1301.

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P1301

ACURA P — Powertrain

Cylinder 1 Misfire

Brand: ACURA
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
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Code

P1301

ALFA ROMEO P — Powertrain

Injector classification fault

Brand: ALFA ROMEO
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
89

Browse 89 ALFA ROMEO manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

P1301

DAEWOO P — Powertrain

TDC SNSR - RANGE / PF MAL

Brand: DAEWOO
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
Repair manuals

Manual library for DAEWOO

75

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Code

P1301

FIAT P — Powertrain

Injector classification fault

Brand: FIAT
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
Repair manuals

Manual library for FIAT

26

Browse 26 FIAT manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

FIAT

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Code

P1301

FORD P — Powertrain

Boost Calibration High

Brand: FORD
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
Your experience will help others
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Keep it short and practical. Up to 500 characters.
Send to email
Code

P1301

HONDA P — Powertrain

Cylinder 1 Misfire

Brand: HONDA
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

P1301

INFINITI P — Powertrain

Cylinder 1 Misfire

Brand: INFINITI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
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Code

P1301

LINCOLN P — Powertrain

Boost Calibration High

Brand: LINCOLN
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
166

Browse 166 LINCOLN manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

P1301

MERCURY P — Powertrain

Boost Calibration High

Brand: MERCURY
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
296

Browse 296 MERCURY manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

P1301

MITSUBISHI P — Powertrain

IG timing adjustment signal

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

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Code

P1301

Other P — Powertrain

Boost Calibration High

Brand: Other
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
9,532

The library contains 9,532 repair and diagnostic manuals. Choose a brand to open the full manual tree by year, model and trim.

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371
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229
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155
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280
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280
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Code

P1301

SAAB P — Powertrain

Torque Limitation Signal, Long Duration

Brand: SAAB
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
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Code

P1301

SUBARU P — Powertrain

Fire Due To Increased Exhaust Temperature

Brand: SUBARU
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty spark plug in cylinder 1
  • Failed or weak ignition coil or ignition module for cylinder 1
  • Clogged, leaking, or electrically open fuel injector for cylinder 1
  • Low compression or mechanical problems (valve, piston, rings) in cylinder 1
  • Fuel delivery or fuel pressure problem (low rail pressure affecting cylinder 1)
  • Vacuum leak or air intake leak near cylinder 1

Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idle or vibration, especially at idle
  • Reduced power, hesitation or stumbling during acceleration
  • Poor fuel economy and increased emissions
  • Possible audible popping/backfire or misfire sensation at specific RPM/load
  • Intermittent fault depending on operating conditions

What to check

  • Read DTCs and freeze-frame data with a scan tool; note misfire counts and operating conditions when DTC set
  • Check live data for cylinder misfire counters/contribution and long/short term fuel trim
  • Inspect spark plug, ignition coil, and boot/connector on cylinder 1 for damage/corrosion
  • Swap ignition coil from cylinder 1 with another cylinder and see if code follows the coil
  • Swap fuel injector with another cylinder (where feasible) to determine if injector follows the code
  • Measure injector resistance and operation (use wiring/actuation tests per service manual)

Signal parameters

  • Misfire counts / cylinder contribution (scan tool)
  • Engine RPM and crankshaft position sensor waveform integrity
  • Ignition coil primary and secondary waveforms (scope) or coil dwell and firing commands
  • Spark plug condition and gap (visual inspection)
  • Injector resistance (ohms) and activation duty cycle (ms) from injector drive
  • Fuel rail pressure (static and dynamic) and fuel trim values (short-term/long-term)

Diagnostic algorithm

  1. Connect a scan tool, record freeze-frame and misfire counters; note operating conditions when code set.
  2. Visually inspect ignition coil, plug, and injector for cylinder 1. Look for corrosion, damaged boots, oil or coolant contamination.
  3. Clear the code and attempt to reproduce. Monitor live misfire counters and cylinder contribution to confirm cylinder 1 is misfiring.
  4. Swap the ignition coil on cylinder 1 with another cylinder. If code moves to that cylinder, replace the coil.
  5. If coil swap does not move the fault, swap the fuel injector with another cylinder (or bench-test injector) to determine if the injector is faulty.
  6. Measure injector resistance and check injector operation with a noid light or oscilloscope. Verify injector wiring continuity and connector condition.
  7. Check fuel pressure at the rail to ensure adequate supply per factory spec. Repair fuel delivery issues if pressure is low or fluctuating.
  8. Perform a wet and/or dry compression test and/or leak-down test on cylinder 1 and compare to the other cylinders. Repair any mechanical faults before replacing ignition/fuel components.
  9. Inspect timing belt/chain and timing marks to confirm correct cam/crank relationship if mechanical timing concern exists.
  10. If no mechanical or primary component faults are found, scope the ignition primary/secondary and crank/cam sensors to verify proper triggering and signal quality.
  11. Repair the failed component(s) found (coil, plug, injector, wiring, mechanical repair). Replace only as needed and verify service manual procedures.
  12. After repair, clear codes and perform a full road test and scan tool verification to ensure misfire no longer repeats; monitor for related codes and proper fuel trims.

Likely causes

  • Faulty ignition coil or spark plug on cylinder 1 (most common)
  • Faulty or clogged fuel injector for cylinder 1
  • Shorted/open wiring or poor connector to coil/injector for cylinder 1
  • Low cylinder compression or internal engine mechanical issue
  • Intermittent sensor signal (crankshaft/camshaft) causing misfire detection

Fault status

⚠️ Status
PCM detected misfire in cylinder 1; MIL on. Troubleshoot ignition, fuel, mechanical, and wiring for cylinder 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours (varies by cause and access to components)
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