Fuel and air

P0279 — Cylinder 7 Fuel Injector Circuit Low

Severity: medium Drive with care, to a shop

What P0279 means

The engine control module fires the cylinder 7 injector by switching its circuit to ground at the right moment, and it monitors the voltage in that circuit. P0279 is set when that voltage stays lower than expected. Common causes are a short to ground, a bad injector coil, poor connections, or a failed driver inside the module.

Symptoms

  • Check engine light on
  • Rough idle
  • Loss of power and sluggish acceleration
  • Increased fuel consumption
  • Misfire on cylinder 7
  • Hesitation or shaking under load

Possible causes

  1. Failed or clogged injector on cylinder 7
  2. Damaged wiring harness or corroded injector connector
  3. Injector wire shorted to ground
  4. Poor ground or low supply voltage to the injector circuit
  5. Failed injector driver inside the PCM
  6. Oil or moisture in the connector

How to diagnose

  1. Scan for codes and freeze-frame data, and look for other injector or misfire codes
  2. Inspect the cylinder 7 injector connector and harness for chafing, heat damage and corrosion
  3. Measure injector coil resistance and compare it with specifications and neighboring injectors
  4. Check for supply voltage and a good ground at the connector
  5. Test the control wire for a short to ground with the PCM disconnected
  6. Listen to the injector with a stethoscope or check the signal with a noid light or scope
  7. Compare fuel trims and cylinder balance, and check fuel pressure
  8. If wiring and injector are good, test the PCM

Common fixes

  • Replace or professionally clean the cylinder 7 injector
  • Repair the damaged wire or replace the connector
  • Clean the terminals and restore the ground connection
  • Replace or reprogram the PCM if a driver fault is confirmed

Questions and answers

What does P0279 mean?

The PCM detected low voltage in the control circuit of the cylinder 7 fuel injector. It points to an electrical fault in the injector, its wiring or the module.

Can I drive with P0279?

Only for a short distance and under light load. Misfires can damage the catalytic converter and waste fuel, so get it checked soon.

What should I check first?

Start with the injector connector and wiring on cylinder 7, then measure the injector coil resistance. These are the most common causes and cheap to check.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.