P0279 medium Severity

P0279: Cylinder 7 Injector Circuit Low voltage detected by PCM

Engine may run rough, reduced power, possible misfire and increased fuel consumption

Overview

Generic OBD-II diagnostic trouble code indicating low voltage or low circuit condition in the fuel injector circuit for cylinder 7, leading to misfire symptoms and driveability issues.

Common Symptoms

  • Check engine light illuminated
  • Rough engine idle
  • Loss of engine power
  • Reduced fuel economy
  • Possible misfire on cylinder 7

Most Common Causes

Faulty or clogged fuel injector #7 high

Injector may be electrically open/shorted or mechanically restricted.

Wiring harness damage or connector corrosion high

Heat, vibration, or moisture can degrade wiring between PCM and injector.

PCM/ECM injector driver output failure medium

Low voltage could originate from a failing driver inside the module.

Poor ground or low supply voltage to injector circuit medium

Loose ground or poor power supply raises resistance, lowering effective injector voltage.

Diagnostic Steps

  1. Retrieve live codes via OBD-II scanner and confirm P0279
    Expected: P0279 present, check for related misfire codes (e.g., P0307)
    Interpretation: Code presence indicates low voltage condition in cylinder 7 injector circuit
  2. Perform visual inspection of injector #7 wiring and connector
    Expected: No corrosion, bent pins, or damaged insulation
    Interpretation: Issues in harness/connectors can cause low voltage signals
  3. Measure voltage at the injector power and ground during cranking
    Expected: Approximately battery voltage at power supply, pulsed signal at ground side
    Interpretation: Low voltage confirms circuit problem upstream (wiring/driver)
  4. Measure injector coil resistance with ignition off
    Expected: Resistance within manufacturer spec (~10-18 ohms typical)
    Interpretation: Out-of-spec resistance indicates internal injector fault
  5. If wiring and injector test good, test PCM output driver function
    Expected: Correct pulsed driver signal from PCM
    Interpretation: Faulty driver suggests PCM repair or replacement

Repair Solutions

Clean or replace fuel injector #7 medium
Estimated Cost: $150 - $450

Cleaning may resolve mechanical clog; replacement required if electrical/mechanical failure.

Repair or replace wiring harness and connectors medium
Estimated Cost: $50 - $250

Repair corrosion/damage; ensure solid ground and power to circuit.

PCM/ECM reprogramming or replacement hard
Estimated Cost: $300 - $1200

Needed if injector driver within PCM has failed; include programming.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Misinterpreting low cylinder performance as ignition fault (spark issues)
  • Assuming fuel pump failure without checking injector circuit
  • Attributing rough idle solely to vacuum leaks

Frequently Asked Questions

Technical definition of P0279 OBD-II Code

Technically, the P0279 code represents Cylinder 7 Injector Circuit Low voltage detected by PCM. It usually points to a fault within the Fuel System.

Is it safe to drive with a P0279 code?

You should treat P0279 as a medium issue. Engine may run rough, reduced power, possible misfire and increased fuel consumption

What are the symptoms of P0279?

Drivers often report: Check engine light illuminated, Rough engine idle, Loss of engine power when this code is present.

Common triggers for the P0279 error

It can be caused by several factors, most notably: Faulty or clogged fuel injector #7, Wiring harness damage or connector corrosion, PCM/ECM injector driver output failure.

How much does it cost to fix P0279?

It depends on what needs to be fixed. Repair or replace wiring harness and connectors repairs are cheaper (~$250), while PCM/ECM reprogramming or replacement repairs are on the higher end (~$1200).

What cars are affected by the P0279 code?

This is a universal code. You might see P0279 on Ford, Chevrolet, Toyota, Honda, Nissan, or any other OBD-II vehicle.

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