P0279
Cylinder 7 Injector A Circuit Low.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 2
- AreaFuel and air metering (injector circuit)
- 79
- FaultThe specific fault in that area
What it means
P0279 means the engine control unit has found the cylinder 7 fuel injector control circuit reading lower than expected. It sets when the monitored voltage or current in that circuit is too low, which points to a short to ground, excess resistance or a fault in the driver. Cylinder 7 only exists on engines with at least eight cylinders, and the cylinder numbering and injector layout depend on the engine.
Symptoms
- Engine warning light on
- Misfire or rough running, usually worse at idle or under load
- Hesitation or loss of power
- Fuel smell or poor economy if the injector is stuck open or running erratically
- Hard starting or extended cranking
- Engine running in a reduced-power or limp mode on some models
Possible causes
- Cylinder 7 injector coil shorted internally or with low winding resistancelikely
- Injector wiring chafed or shorted to ground between the injector and the control unitlikely
- Corroded, loose or damaged injector connector or terminalslikely
- Water or fuel contamination in the harness or connector causing leakage to groundpossible
- Faulty injector driver inside the engine control unitrare
- Harness damage elsewhere, for example at a bulkhead plug or a rubbed section near the enginepossible
- Outdated or faulty control unit software where a manufacturer bulletin lists this faultrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting load, rpm and temperature when it set, and check for other injector or misfire codes
- Confirm which physical cylinder is number 7 on this engine using the manufacturer's layout, as numbering varies by model and bank
- Visually inspect the cylinder 7 injector connector and nearby harness for chafing, heat damage, oil or fuel contamination, corrosion and bent or pushed-back pins
- Check the injector coil resistance against the manufacturer's specification with the connector unplugged
- Test the injector circuit wiring for a short to ground and for continuity and resistance back to the control unit, with the control unit disconnected as the procedure requires
- Check the supply voltage and ground to the injector, and look at the injector control signal with a suitable scope or live data
- Swap the injector with one from another cylinder, clear the code and see whether the fault follows the injector
- Check for relevant software updates or technical bulletins for the engine, and only suspect the control unit once the wiring and injector have been cleared
How to fix
- Replace the cylinder 7 injector if its resistance or operation is out of specification
- Repair or replace the damaged section of wiring, and secure and protect it against further rubbing
- Clean, repair or replace the injector connector and terminals, and make sure the connector locks properly
- Dry out and fix the source of any water or fuel ingress into the harness or connector
- Repair or replace the engine control unit only after confirming the driver fault, then carry out any required programming
- Apply a manufacturer-approved software update if a known calibration fault is the cause
Can I keep driving?
The car may be driven carefully a short distance, but get it checked soon. A misfiring or badly running cylinder can overheat the catalytic converter, so avoid heavy loads, and stop if the engine runs rough or flashes the warning light.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.