Fuel and air

P02A2 — Cylinder 3 Fuel Trim at Maximum Limit

Severity: medium Drive with care, to a shop

What P02A2 means

The engine control unit monitors the air-fuel mixture and adjusts injection for each cylinder to keep it correct. P02A2 is set when the correction for cylinder 3 has reached its maximum and the mixture is still off. That means this cylinder is running too lean or too rich by more than the ECU can compensate for.

Symptoms

  • Check Engine light on
  • Rough idle
  • Misfires or stumbling
  • Weak acceleration, loss of power
  • Higher fuel consumption
  • Hesitation under load

Possible causes

  1. Faulty or clogged cylinder 3 fuel injector
  2. Vacuum or intake leak near cylinder 3 (manifold gasket, hose, seal)
  3. Wiring or connector fault at the injector
  4. Faulty oxygen sensor or mass airflow (MAF) sensor
  5. Low fuel pressure from the pump, filter or regulator
  6. Ignition or compression problem in cylinder 3 (plug, coil, valve)

How to diagnose

  1. Read codes and freeze frame data, and look for misfire codes (P0303) or other fuel trim codes.
  2. View short and long term fuel trims at idle and around 2,500 rpm: a large positive value points to a lean condition, negative to rich.
  3. Inspect the cylinder 3 injector connector and wiring, and check power and control signal.
  4. Look for intake leaks with a smoke machine and inspect hoses and the manifold gasket.
  5. Measure fuel pressure and compare it with the manufacturer spec.
  6. Compare cylinders by swapping the injector or coil with a neighbor and see if the fault follows.
  7. Check the spark plug, coil and compression of cylinder 3.
  8. Evaluate oxygen sensor and MAF readings.

Common fixes

  • Clean or replace the cylinder 3 injector
  • Repair intake leaks: manifold gasket, hoses, seals
  • Repair the injector wiring or connector
  • Replace a faulty oxygen or MAF sensor
  • Replace the fuel filter, pump or pressure regulator if pressure is low
  • Replace the plug or coil, or repair the engine if compression is poor

Questions and answers

What does P02A2 mean?

The ECU can't correct the mixture in cylinder 3 because its fuel trim has hit the limit. An injector problem or an air leak is the most common reason.

Can I drive with P02A2?

Briefly and gently, avoiding heavy loads. If misfires start, stop to avoid damaging the catalytic converter.

Where should I start diagnosing P02A2?

Check the fuel trims first, then inspect the cylinder 3 injector, its connector and any possible air leaks near that cylinder.

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.