Code
P0280
HUMMER
P — Powertrain
Cylinder 7 Injector Circuit High
AI status
Completed
Completed
100%
Causes
- Open or damaged wiring in cylinder 7 injector circuit
- Short to battery voltage on the injector feed or driver wire
- Corroded, bent or pushed-out injector connector pins
- Failed fuel injector (internal short or wiring fault)
- Faulty ECM/PCM injector driver
- Poor or missing ground or power supply related to injector circuit
Symptoms
- Check Engine Light illuminated (DTC P0280)
- Rough idle or vibration, especially under load
- Cylinder 7 misfire codes may also appear (P0307)
- Reduced engine power, hesitation or stalling
- Hard starting or poor fuel economy
What to check
- Retrieve freeze frame and live data to confirm conditions when fault set
- Visual inspection of injector connector for corrosion, damage, or pushed-out pins
- Check continuity and insulation of wiring between cylinder 7 injector and ECM
- Measure injector supply voltage at the connector with key ON (should be ~battery voltage)
- Measure injector driver voltage while cranking/running (should pull near 0V when activated)
- Measure injector coil resistance with connector disconnected
Signal parameters
- Key ON (engine off): injector supply pin ~11–14 V (battery voltage)
- When ECM energizes injector: driver pin should be pulled near 0–1 V (ground switching)
- Idle/normal pulse width: typically 1–10 ms depending on load and rpm (varies by engine)
- Injector coil resistance (typical gasoline injector): ~1–16 Ω (manufacturer varies) — consult service data
- Expected injector current during pulse: up to a few amps (varies by injector type)
- Fault condition: driver/side voltage remains near battery voltage during command (indicates 'High')
Diagnostic algorithm
- Read ECU codes and freeze-frame data; confirm P0280 and note engine conditions.
- Perform a visual inspection of harness/connector at cylinder 7 for damage, corrosion or water intrusion.
- With ignition OFF, disconnect injector connector and measure injector coil resistance. Compare to specified range.
- Inspect connector pins for continuity to the ECM pin for cylinder 7 (check for open or short to other circuits).
- With ignition ON or while cranking, back-probe the injector connector: verify supply (battery) and driver voltages and look for switching to ground when injection is commanded. Use an oscilloscope if available to view waveform.
- Check for a short to battery on the driver lead (use ohmmeter/power probe with care). A very high or battery-level voltage when driver should be low indicates short or open-high condition.
- Swap the suspect injector with a known-good injector from another cylinder and retest: if the code follows the injector, replace the injector; if it stays with cylinder 7, suspect wiring or ECM.
- Inspect/repair wiring connectors, repair any damaged wires, clean/replace corroded connectors and pins.
- If wiring and injector check good, test or replace ECM/PCM or have ECM bench-tested/replaced as a last resort.
- Clear codes and road-test to verify repair; re-scan to confirm P0280 does not return.
Likely causes
- Connector corrosion or pin damage at cylinder 7 injector
- Open/ intermittent wiring between injector and ECM
- Injector internal failure (short/high resistance to supply)
- Short to battery voltage on the driver lead
- ECM driver transistor fault
Fault status
Status
The ECM detected abnormally high voltage on the Cylinder 7 fuel injector driver circuit. This indicates the injector circuit is not being pulled to the expected voltage when commanded (open, short to battery, connector fault, failed injector, or ECM driver fault).
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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