Fuel and air

P026C — Fuel Injection Quantity Lower Than Expected

Severity: medium Drive with care, to a shop

What P026C means

The engine control module compares the fuel quantity it commands with what is actually delivered, estimated from rail pressure, fuel trims and crankshaft speed variation. When one cylinder consistently receives less fuel than commanded, P026C is stored. The cause may be the injector itself, its wiring, low fuel pressure or a software calibration problem.

Symptoms

  • Check Engine Light on
  • Engine misfires
  • Rough idle
  • Reduced power and sluggish acceleration
  • Worse fuel economy
  • Increased exhaust emissions

Possible causes

  1. Faulty or clogged fuel injector
  2. Low fuel pressure: weak pump, clogged filter or bad regulator
  3. Injector circuit problem: open circuit, poor connection or corroded connector
  4. ECM software or calibration issue
  5. Contaminated or poor-quality fuel

How to diagnose

  1. Read all codes and freeze-frame data, noting any misfire or fuel trim codes
  2. Review short-term and long-term fuel trims at idle and under load
  3. Measure fuel pressure and compare it with the manufacturer's specification
  4. Inspect injector wiring and connectors for damage, shorts to ground, opens and corrosion
  5. Test injector coil resistance and check the drive signal with a scope or noid light
  6. Run a scan tool injector balance or cylinder contribution test
  7. Check the fuel filter and pump output, and consider fuel quality if in doubt
  8. Check for ECM software updates for your vehicle

Common fixes

  • Clean professionally or replace the faulty injector
  • Repair damaged wiring and connectors
  • Replace the fuel filter and, if needed, the fuel pump
  • Update or reflash the ECM software
  • Drain contaminated fuel and refill with fresh fuel

Questions and answers

What does P026C mean?

The ECM found that a cylinder is getting less fuel than it commanded. Common causes are an injector problem, low fuel pressure or injector wiring faults.

Can I drive with P026C?

Briefly, yes, but don't put it off. A lean cylinder and misfires can damage the catalytic converter and the engine.

How do I fix P026C?

Start by checking fuel pressure, fuel trims and injector wiring. If those are fine, clean or replace the injector and update the ECM software if needed.

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.