Fuel and air

P02C6 — Cylinder 12 Fuel Trim at Maximum Limit

Severity: medium Drive with care, to a shop

What P02C6 means

The engine control module constantly adjusts fuel delivery for each cylinder to keep the air-fuel mixture near ideal. P02C6 means the correction for cylinder 12 has hit its programmed limit, so the module can't compensate any further. The cause is usually a fuel delivery problem, extra air entering the engine, or bad sensor feedback.

Symptoms

  • Check Engine light on
  • Rough or uneven idle
  • Reduced power and sluggish acceleration
  • Increased fuel consumption
  • Hesitation or stumbling under throttle
  • Possible misfires
  • Emissions problems

Possible causes

  1. Faulty or clogged cylinder 12 fuel injector
  2. Vacuum or intake air leak near cylinder 12
  3. Failing oxygen, MAF or MAP sensor
  4. Low fuel pressure from a weak pump or clogged filter
  5. Compression or ignition problem in cylinder 12
  6. Wiring or connector fault at the injector
  7. Exhaust leak skewing oxygen sensor readings

How to diagnose

  1. Scan all codes and review freeze frame data for related mixture or misfire codes
  2. Check short-term and long-term fuel trims at idle and under load
  3. Inspect intake ducts, gaskets and vacuum hoses for leaks
  4. Inspect the cylinder 12 injector connector and wiring, and measure injector resistance
  5. Compare cylinders with an injector balance test and misfire counters
  6. Measure fuel pressure against the manufacturer spec
  7. Check MAF and oxygen sensor readings and look for exhaust leaks
  8. If everything else checks out, run a compression test on cylinder 12

Common fixes

  • Clean or replace the cylinder 12 injector
  • Repair intake or vacuum leaks and replace damaged hoses or gaskets
  • Replace the faulty sensor (O2, MAF or MAP)
  • Replace the fuel filter or pump if pressure is low
  • Repair the injector wiring or connector
  • Fix internal engine problems if compression is low

Questions and answers

What does P02C6 mean?

The ECM has pushed the fuel trim for cylinder 12 to its limit and can't correct the mixture any further. Fuel delivery, air intake or sensor readings are causing the mixture to deviate.

Can I drive with code P02C6?

Briefly and gently, yes, but get it checked soon. Running with the wrong mixture for long increases fuel use and can damage the catalytic converter.

What should I check first?

Look at the fuel trim data and inspect the intake for air leaks, then test the cylinder 12 injector and fuel pressure.

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.