Fuel and air

P02C3 — Cylinder 11 Fuel Trim at Minimum Limit

Severity: medium Drive with care, to a shop

What P02C3 means

The engine control unit constantly adjusts fuel delivery for each cylinder based on air/fuel ratio sensor feedback. P02C3 means the correction for cylinder 11 has hit its lower limit: the ECU is removing as much fuel as it can, yet the mixture still reads rich. The usual suspects are an injector that delivers too much fuel or a sensor giving wrong readings.

Symptoms

  • Check Engine light on
  • Rough idle or engine shudder
  • Fuel smell or black smoke from the exhaust
  • Poor fuel economy
  • Hesitation under throttle
  • Possible misfires

Possible causes

  1. Leaking or stuck-open fuel injector on cylinder 11
  2. Injector flowing too much or fouled with deposits
  3. Fuel pressure too high (regulator or return line fault)
  4. Faulty or contaminated air/fuel ratio or oxygen sensor on that cylinder bank
  5. Damaged injector wiring or connector, poor ground
  6. Wrong readings from the mass airflow or manifold pressure sensor
  7. ECU fault (rare)

How to diagnose

  1. Read all codes and freeze frame data and look for related mixture or misfire codes
  2. Use a scan tool to compare fuel trims by bank and by cylinder with neighboring cylinders
  3. Inspect the cylinder 11 injector connector and harness and measure the injector coil resistance
  4. Check fuel pressure and how well it holds after shutdown
  5. Check the air/fuel sensors and the airflow sensor in live data
  6. Pull the cylinder 11 spark plug: black sooty deposits point to a rich mixture
  7. Test the injector for leakage and spray pattern, or use a cylinder balance test
  8. After repair, clear adaptations and confirm trims on a warm engine

Common fixes

  • Clean or replace the cylinder 11 injector
  • Replace the fuel pressure regulator or fix the cause of high pressure
  • Replace a faulty air/fuel ratio sensor or airflow sensor
  • Repair injector wiring and connectors
  • Replace the spark plug and change the oil if it is diluted with fuel

Questions and answers

What does P02C3 mean?

The ECU has pushed the fuel trim for cylinder 11 to its lower limit. It is removing as much fuel as it can, but the mixture is still rich.

Can I drive with P02C3?

Briefly, yes, but get it fixed soon. Excess fuel can damage the catalytic converter and thin out the engine oil.

Why does the code point to cylinder 11?

Cylinder numbers this high appear on V12 and similar engines. The ECU tracks the mixture per cylinder, so the injector of that cylinder is the first suspect.

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.