Code
P0263
Generic
P — Powertrain
Cylinder 1 Contribution/Balance
Views:
UK: 31
EN: 64
RU: 77
AI status
Completed
Completed
100%
Causes
- Faulty or clogged fuel injector for cylinder 1
- Ignition fault (bad spark plug, ignition coil or secondary wiring) on cylinder 1
- Low compression or mechanical damage in cylinder 1 (valve, piston, rings)
- Fuel pressure or rail supply problem reducing injector flow
- Vacuum, intake or exhaust leak affecting cylinder 1
- Wiring or connector fault in injector or ignition circuit
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or engine vibration
- Reduced power, hesitation or stumble under acceleration
- Increased fuel consumption and higher emissions
- Possible misfire code(s) for cylinder 1 (e.g., P0301)
What to check
- Read all stored/active codes and freeze frame data with a scan tool
- Check for associated codes (P0301, P0201, fuel trim codes, etc.)
- Live data: monitor misfire counts, short and long term fuel trim, and cylinder contribution values
- Inspect spark plug, ignition coil and secondary wiring on cylinder 1
- Visually inspect injector connector and wiring for corrosion or damage
- Measure fuel rail pressure and verify within spec
Signal parameters
- Cylinder contribution or balance percentage for cylinder 1
- Cylinder-specific misfire count (cyl 1)
- Short-term and long-term fuel trim (STFT/LTFT)
- Fuel rail pressure (psi/bar)
- Injector pulse width (ms) for cylinder 1
- Ignition dwell or coil primary current (if available)
Diagnostic algorithm
- Retrieve P0263 and any related codes; record freeze frame and live data.
- Inspect spark plug and ignition coil for cylinder 1; replace if fouled or damaged.
- Swap the ignition coil from cylinder 1 with another cylinder; clear codes and re-run. If misfire or contribution issue moves, suspect coil/spark or wiring.
- Swap the fuel injector from cylinder 1 with another cylinder (or swap injector connectors) and retest. If problem follows the injector, replace or service injector.
- Measure injector resistance and pulse width; use a noid light or oscilloscope to verify injector drive and waveform.
- Check fuel rail pressure under load to ensure proper supply; inspect for clogged fuel filter or failing pump/regulator.
- Perform a compression test and/or leak-down on cylinder 1 to rule out mechanical causes.
- Inspect for vacuum/intake manifold leaks or exhaust leaks near cylinder 1 that could affect combustion.
- Inspect wiring harness and connectors for damage, corrosion, or poor ground for injector and ignition circuits. Repair as needed.
- If tests are inconclusive, monitor more detailed waveforms (ignition and injector) and consider bench-testing suspect components or consulting manufacturer-specific service information. Clear codes and road test to verify repair.
Likely causes
- Faulty injector (sticking, clogged or electrically open) on cylinder 1
- Faulty ignition coil or spark plug on cylinder 1
- Low cylinder compression (worn rings, leaking valve)
- Shorted/open injector wiring or poor connector
- Low fuel rail pressure or failing fuel pump/regulator
- Vacuum leak or intake manifold gasket leak near cylinder 1
Fault status
Status
PCM detected a reduced contribution/balance for cylinder 1 and set MIL. Code stored with freeze-frame and live data. Further testing required to isolate electrical, fuel, ignition, or mechanical causes.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0263
GWM
P — Powertrain
- Invalidly balanced 1 cylinder
Views:
UK: 11
EN: 25
RU: 31
AI status
Completed
Completed
100%
Causes
- Faulty or clogged fuel injector for cylinder 1
- Ignition fault (bad spark plug, ignition coil or secondary wiring) on cylinder 1
- Low compression or mechanical damage in cylinder 1 (valve, piston, rings)
- Fuel pressure or rail supply problem reducing injector flow
- Vacuum, intake or exhaust leak affecting cylinder 1
- Wiring or connector fault in injector or ignition circuit
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or engine vibration
- Reduced power, hesitation or stumble under acceleration
- Increased fuel consumption and higher emissions
- Possible misfire code(s) for cylinder 1 (e.g., P0301)
What to check
- Read all stored/active codes and freeze frame data with a scan tool
- Check for associated codes (P0301, P0201, fuel trim codes, etc.)
- Live data: monitor misfire counts, short and long term fuel trim, and cylinder contribution values
- Inspect spark plug, ignition coil and secondary wiring on cylinder 1
- Visually inspect injector connector and wiring for corrosion or damage
- Measure fuel rail pressure and verify within spec
Signal parameters
- Cylinder contribution or balance percentage for cylinder 1
- Cylinder-specific misfire count (cyl 1)
- Short-term and long-term fuel trim (STFT/LTFT)
- Fuel rail pressure (psi/bar)
- Injector pulse width (ms) for cylinder 1
- Ignition dwell or coil primary current (if available)
Diagnostic algorithm
- Retrieve P0263 and any related codes; record freeze frame and live data.
- Inspect spark plug and ignition coil for cylinder 1; replace if fouled or damaged.
- Swap the ignition coil from cylinder 1 with another cylinder; clear codes and re-run. If misfire or contribution issue moves, suspect coil/spark or wiring.
- Swap the fuel injector from cylinder 1 with another cylinder (or swap injector connectors) and retest. If problem follows the injector, replace or service injector.
- Measure injector resistance and pulse width; use a noid light or oscilloscope to verify injector drive and waveform.
- Check fuel rail pressure under load to ensure proper supply; inspect for clogged fuel filter or failing pump/regulator.
- Perform a compression test and/or leak-down on cylinder 1 to rule out mechanical causes.
- Inspect for vacuum/intake manifold leaks or exhaust leaks near cylinder 1 that could affect combustion.
- Inspect wiring harness and connectors for damage, corrosion, or poor ground for injector and ignition circuits. Repair as needed.
- If tests are inconclusive, monitor more detailed waveforms (ignition and injector) and consider bench-testing suspect components or consulting manufacturer-specific service information. Clear codes and road test to verify repair.
Likely causes
- Faulty injector (sticking, clogged or electrically open) on cylinder 1
- Faulty ignition coil or spark plug on cylinder 1
- Low cylinder compression (worn rings, leaking valve)
- Shorted/open injector wiring or poor connector
- Low fuel rail pressure or failing fuel pump/regulator
- Vacuum leak or intake manifold gasket leak near cylinder 1
Fault status
Status
PCM detected a reduced contribution/balance for cylinder 1 and set MIL. Code stored with freeze-frame and live data. Further testing required to isolate electrical, fuel, ignition, or mechanical causes.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
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Code
P0263
HUMMER
P — Powertrain
Cylinder 1 Contribution/Balance Fault
Views:
UK: 14
EN: 34
RU: 50
AI status
Completed
Completed
100%
Causes
- Faulty or clogged fuel injector for cylinder 1
- Ignition fault (bad spark plug, ignition coil or secondary wiring) on cylinder 1
- Low compression or mechanical damage in cylinder 1 (valve, piston, rings)
- Fuel pressure or rail supply problem reducing injector flow
- Vacuum, intake or exhaust leak affecting cylinder 1
- Wiring or connector fault in injector or ignition circuit
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or engine vibration
- Reduced power, hesitation or stumble under acceleration
- Increased fuel consumption and higher emissions
- Possible misfire code(s) for cylinder 1 (e.g., P0301)
What to check
- Read all stored/active codes and freeze frame data with a scan tool
- Check for associated codes (P0301, P0201, fuel trim codes, etc.)
- Live data: monitor misfire counts, short and long term fuel trim, and cylinder contribution values
- Inspect spark plug, ignition coil and secondary wiring on cylinder 1
- Visually inspect injector connector and wiring for corrosion or damage
- Measure fuel rail pressure and verify within spec
Signal parameters
- Cylinder contribution or balance percentage for cylinder 1
- Cylinder-specific misfire count (cyl 1)
- Short-term and long-term fuel trim (STFT/LTFT)
- Fuel rail pressure (psi/bar)
- Injector pulse width (ms) for cylinder 1
- Ignition dwell or coil primary current (if available)
Diagnostic algorithm
- Retrieve P0263 and any related codes; record freeze frame and live data.
- Inspect spark plug and ignition coil for cylinder 1; replace if fouled or damaged.
- Swap the ignition coil from cylinder 1 with another cylinder; clear codes and re-run. If misfire or contribution issue moves, suspect coil/spark or wiring.
- Swap the fuel injector from cylinder 1 with another cylinder (or swap injector connectors) and retest. If problem follows the injector, replace or service injector.
- Measure injector resistance and pulse width; use a noid light or oscilloscope to verify injector drive and waveform.
- Check fuel rail pressure under load to ensure proper supply; inspect for clogged fuel filter or failing pump/regulator.
- Perform a compression test and/or leak-down on cylinder 1 to rule out mechanical causes.
- Inspect for vacuum/intake manifold leaks or exhaust leaks near cylinder 1 that could affect combustion.
- Inspect wiring harness and connectors for damage, corrosion, or poor ground for injector and ignition circuits. Repair as needed.
- If tests are inconclusive, monitor more detailed waveforms (ignition and injector) and consider bench-testing suspect components or consulting manufacturer-specific service information. Clear codes and road test to verify repair.
Likely causes
- Faulty injector (sticking, clogged or electrically open) on cylinder 1
- Faulty ignition coil or spark plug on cylinder 1
- Low cylinder compression (worn rings, leaking valve)
- Shorted/open injector wiring or poor connector
- Low fuel rail pressure or failing fuel pump/regulator
- Vacuum leak or intake manifold gasket leak near cylinder 1
Fault status
Status
PCM detected a reduced contribution/balance for cylinder 1 and set MIL. Code stored with freeze-frame and live data. Further testing required to isolate electrical, fuel, ignition, or mechanical causes.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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