Code
P0286
Generic
P — Powertrain
Cylinder 9 Injector A Circuit High
AI status
Completed
Completed
100%
Causes
- Corroded, contaminated, or loose injector connector
- Damaged wiring harness (short to battery/ignition feed or high resistance)
- Internal short or failure inside the injector solenoid
- Poor or missing ground in the injector circuit or nearby ground strap
- Faulty ECM/PCM injector driver (output stage) or intermittent internal failure
- Water intrusion or oil contamination in the connector or harness
Symptoms
- Check Engine Light with stored P0286 code
- Rough idle or misfire on cylinder 9
- Loss of power, hesitation or increased fuel consumption
- Hard starting or extended cranking in some conditions
- Smoke or unusual exhaust behavior (diesel engines)
- Intermittent operation if connector/harness is intermittent
What to check
- Read freeze-frame and permanent data; record conditions when the code set (RPM, temp, load).
- Visual inspection of injector 9 connector and wiring for damage, corrosion, oil/water intrusion and proper seating.
- Check for corrosion/loose pins and secure connector; inspect for melted insulation or exposed conductors.
- With ignition OFF, measure injector coil resistance at the injector (compare to spec or other cylinders).
- With ignition ON (engine OFF), check for battery voltage on the supply pin of the injector connector.
- Back-probe the injector connector during cranking/idle to verify driver switching (use a lab scope or high-speed multimeter).
Signal parameters
- Injector coil resistance: manufacturer-specific. Typical ranges: low-impedance injectors ~0.5–3 Ω, high-impedance injectors ~10–18 Ω. Compare to other cylinders and OEM spec.
- Connector supply: ~12 V (battery voltage) present on the constant power pin with ignition ON.
- Driver behavior: ECM usually uses a low-side switch. Idle/no-fire state: injector output at or near battery voltage; during injection the driver pulls the pin close to 0 V.
- Pulse width: typical injection pulse widths are in the hundreds to a few thousand microseconds (µs) depending on engine load and rpm — use oscilloscope for exact timing.
- Current draw: depends on injector type; low-impedance injectors can draw several amps during activation. Excessive current or no switching indicates fault.
Diagnostic algorithm
- Retrieve trouble code, freeze-frame and history. Note operating conditions when the fault occurred.
- Perform a thorough visual inspection of cylinder 9 injector connector and wiring harness for damage, melting, corrosion, or contamination. Repair obvious damage.
- With ignition OFF, disconnect injector connector. Measure injector coil resistance across injector pins. Compare to OEM spec or to another known-good cylinder. If out of range, consider replacing the injector.
- With connector disconnected and ignition ON (engine OFF), verify battery voltage on the injector supply pin. If no supply, check fuses/relays and upstream feed circuits.
- Reconnect and back-probe the injector connector. Crank or run engine and observe signal with oscilloscope or duty-cycle meter. Verify the driver is switching to ground during injection and that voltage levels are within expected ranges.
- Check continuity between the injector connector control pin and the ECM connector pin. Measure for high resistance, opens, or shorts to battery or ground. Wiggle harness during test to detect intermittent faults.
- Inspect and test engine/chassis grounds related to the injector circuit. Clean and tighten ground connections if high resistance is found.
- If wiring and injector check OK, swap injector 9 with another cylinder's injector (if identical) and see if the code or misfire follows the injector. If it follows, replace the injector.
- If problem remains at cylinder 9 after injector swap and wiring checks are good, suspect ECM driver failure. Confirm with bench testing or professional ECU diagnostic/test equipment before replacing the module.
- After repairs, clear codes and perform a test drive under the same conditions to confirm the fault does not return. Re-scan for pending/new codes.
Likely causes
- Corroded/contaminated connector or pin corrosion at cylinder 9 injector
- Broken or chafed wire near the injector or along harness to the ECU
- Failed injector (internal short/high leakage current)
- Poor ground at engine block or wiring ground point for injector circuit
- Occasional ECM driver failure (less common than harness/connector faults)
Fault status
Status
Injector circuit high for Cylinder 9 (Injector A): ECM detects higher-than-expected voltage or abnormal electrical condition on injector drive circuit. Possible causes include connector/harness damage, failed injector, poor ground, or ECM driver fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Code
P0286
GWM
P — Powertrain
- High Cylinder Injector 9 Circuit High
AI status
Completed
Completed
100%
Causes
- Corroded, contaminated, or loose injector connector
- Damaged wiring harness (short to battery/ignition feed or high resistance)
- Internal short or failure inside the injector solenoid
- Poor or missing ground in the injector circuit or nearby ground strap
- Faulty ECM/PCM injector driver (output stage) or intermittent internal failure
- Water intrusion or oil contamination in the connector or harness
Symptoms
- Check Engine Light with stored P0286 code
- Rough idle or misfire on cylinder 9
- Loss of power, hesitation or increased fuel consumption
- Hard starting or extended cranking in some conditions
- Smoke or unusual exhaust behavior (diesel engines)
- Intermittent operation if connector/harness is intermittent
What to check
- Read freeze-frame and permanent data; record conditions when the code set (RPM, temp, load).
- Visual inspection of injector 9 connector and wiring for damage, corrosion, oil/water intrusion and proper seating.
- Check for corrosion/loose pins and secure connector; inspect for melted insulation or exposed conductors.
- With ignition OFF, measure injector coil resistance at the injector (compare to spec or other cylinders).
- With ignition ON (engine OFF), check for battery voltage on the supply pin of the injector connector.
- Back-probe the injector connector during cranking/idle to verify driver switching (use a lab scope or high-speed multimeter).
Signal parameters
- Injector coil resistance: manufacturer-specific. Typical ranges: low-impedance injectors ~0.5–3 Ω, high-impedance injectors ~10–18 Ω. Compare to other cylinders and OEM spec.
- Connector supply: ~12 V (battery voltage) present on the constant power pin with ignition ON.
- Driver behavior: ECM usually uses a low-side switch. Idle/no-fire state: injector output at or near battery voltage; during injection the driver pulls the pin close to 0 V.
- Pulse width: typical injection pulse widths are in the hundreds to a few thousand microseconds (µs) depending on engine load and rpm — use oscilloscope for exact timing.
- Current draw: depends on injector type; low-impedance injectors can draw several amps during activation. Excessive current or no switching indicates fault.
Diagnostic algorithm
- Retrieve trouble code, freeze-frame and history. Note operating conditions when the fault occurred.
- Perform a thorough visual inspection of cylinder 9 injector connector and wiring harness for damage, melting, corrosion, or contamination. Repair obvious damage.
- With ignition OFF, disconnect injector connector. Measure injector coil resistance across injector pins. Compare to OEM spec or to another known-good cylinder. If out of range, consider replacing the injector.
- With connector disconnected and ignition ON (engine OFF), verify battery voltage on the injector supply pin. If no supply, check fuses/relays and upstream feed circuits.
- Reconnect and back-probe the injector connector. Crank or run engine and observe signal with oscilloscope or duty-cycle meter. Verify the driver is switching to ground during injection and that voltage levels are within expected ranges.
- Check continuity between the injector connector control pin and the ECM connector pin. Measure for high resistance, opens, or shorts to battery or ground. Wiggle harness during test to detect intermittent faults.
- Inspect and test engine/chassis grounds related to the injector circuit. Clean and tighten ground connections if high resistance is found.
- If wiring and injector check OK, swap injector 9 with another cylinder's injector (if identical) and see if the code or misfire follows the injector. If it follows, replace the injector.
- If problem remains at cylinder 9 after injector swap and wiring checks are good, suspect ECM driver failure. Confirm with bench testing or professional ECU diagnostic/test equipment before replacing the module.
- After repairs, clear codes and perform a test drive under the same conditions to confirm the fault does not return. Re-scan for pending/new codes.
Likely causes
- Corroded/contaminated connector or pin corrosion at cylinder 9 injector
- Broken or chafed wire near the injector or along harness to the ECU
- Failed injector (internal short/high leakage current)
- Poor ground at engine block or wiring ground point for injector circuit
- Occasional ECM driver failure (less common than harness/connector faults)
Fault status
Status
Injector circuit high for Cylinder 9 (Injector A): ECM detects higher-than-expected voltage or abnormal electrical condition on injector drive circuit. Possible causes include connector/harness damage, failed injector, poor ground, or ECM driver fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
Similar codes
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Code
P0286
HUMMER
P — Powertrain
Cylinder 9 Injector Circuit High
AI status
Completed
Completed
100%
Causes
- Corroded, contaminated, or loose injector connector
- Damaged wiring harness (short to battery/ignition feed or high resistance)
- Internal short or failure inside the injector solenoid
- Poor or missing ground in the injector circuit or nearby ground strap
- Faulty ECM/PCM injector driver (output stage) or intermittent internal failure
- Water intrusion or oil contamination in the connector or harness
Symptoms
- Check Engine Light with stored P0286 code
- Rough idle or misfire on cylinder 9
- Loss of power, hesitation or increased fuel consumption
- Hard starting or extended cranking in some conditions
- Smoke or unusual exhaust behavior (diesel engines)
- Intermittent operation if connector/harness is intermittent
What to check
- Read freeze-frame and permanent data; record conditions when the code set (RPM, temp, load).
- Visual inspection of injector 9 connector and wiring for damage, corrosion, oil/water intrusion and proper seating.
- Check for corrosion/loose pins and secure connector; inspect for melted insulation or exposed conductors.
- With ignition OFF, measure injector coil resistance at the injector (compare to spec or other cylinders).
- With ignition ON (engine OFF), check for battery voltage on the supply pin of the injector connector.
- Back-probe the injector connector during cranking/idle to verify driver switching (use a lab scope or high-speed multimeter).
Signal parameters
- Injector coil resistance: manufacturer-specific. Typical ranges: low-impedance injectors ~0.5–3 Ω, high-impedance injectors ~10–18 Ω. Compare to other cylinders and OEM spec.
- Connector supply: ~12 V (battery voltage) present on the constant power pin with ignition ON.
- Driver behavior: ECM usually uses a low-side switch. Idle/no-fire state: injector output at or near battery voltage; during injection the driver pulls the pin close to 0 V.
- Pulse width: typical injection pulse widths are in the hundreds to a few thousand microseconds (µs) depending on engine load and rpm — use oscilloscope for exact timing.
- Current draw: depends on injector type; low-impedance injectors can draw several amps during activation. Excessive current or no switching indicates fault.
Diagnostic algorithm
- Retrieve trouble code, freeze-frame and history. Note operating conditions when the fault occurred.
- Perform a thorough visual inspection of cylinder 9 injector connector and wiring harness for damage, melting, corrosion, or contamination. Repair obvious damage.
- With ignition OFF, disconnect injector connector. Measure injector coil resistance across injector pins. Compare to OEM spec or to another known-good cylinder. If out of range, consider replacing the injector.
- With connector disconnected and ignition ON (engine OFF), verify battery voltage on the injector supply pin. If no supply, check fuses/relays and upstream feed circuits.
- Reconnect and back-probe the injector connector. Crank or run engine and observe signal with oscilloscope or duty-cycle meter. Verify the driver is switching to ground during injection and that voltage levels are within expected ranges.
- Check continuity between the injector connector control pin and the ECM connector pin. Measure for high resistance, opens, or shorts to battery or ground. Wiggle harness during test to detect intermittent faults.
- Inspect and test engine/chassis grounds related to the injector circuit. Clean and tighten ground connections if high resistance is found.
- If wiring and injector check OK, swap injector 9 with another cylinder's injector (if identical) and see if the code or misfire follows the injector. If it follows, replace the injector.
- If problem remains at cylinder 9 after injector swap and wiring checks are good, suspect ECM driver failure. Confirm with bench testing or professional ECU diagnostic/test equipment before replacing the module.
- After repairs, clear codes and perform a test drive under the same conditions to confirm the fault does not return. Re-scan for pending/new codes.
Likely causes
- Corroded/contaminated connector or pin corrosion at cylinder 9 injector
- Broken or chafed wire near the injector or along harness to the ECU
- Failed injector (internal short/high leakage current)
- Poor ground at engine block or wiring ground point for injector circuit
- Occasional ECM driver failure (less common than harness/connector faults)
Fault status
Status
Injector circuit high for Cylinder 9 (Injector A): ECM detects higher-than-expected voltage or abnormal electrical condition on injector drive circuit. Possible causes include connector/harness damage, failed injector, poor ground, or ECM driver fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Repair manuals
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