Fuel and air

P02AF — Cylinder 6 Fuel Trim at Minimum Limit (Mixture Too Rich)

Severity: medium Drive with care, to a shop

What P02AF means

The engine control unit monitors the air-fuel mixture and adjusts injector timing for each cylinder. P02AF means the correction for cylinder 6 has hit its lower limit: the ECU is already removing as much fuel as it can, yet the mixture is still rich. Too much fuel is reaching that cylinder, or less air is arriving than the ECU expects.

Symptoms

  • Check engine light on
  • Rough idle, possible misfire on cylinder 6
  • Higher fuel consumption
  • Fuel smell or black smoke from the exhaust
  • Reduced power and sluggish acceleration
  • Higher exhaust emissions

Possible causes

  1. Leaking or stuck-open fuel injector on cylinder 6
  2. Fuel pressure too high (regulator or return line problem)
  3. Faulty MAF or MAP sensor giving a wrong air reading
  4. Faulty oxygen or wideband sensor reporting the mixture incorrectly
  5. Wiring or connector fault at the cylinder 6 injector
  6. Mechanical problem in the cylinder (wear, low compression, oil in the combustion chamber)
  7. ECU fault (rare)

How to diagnose

  1. Read all codes and freeze-frame data, and look for other mixture or misfire codes
  2. Check short-term and long-term fuel trims and the MAF/MAP readings on a scan tool
  3. Test fuel pressure and how well it holds after shutdown
  4. Inspect the cylinder 6 injector connector and wiring, and measure injector resistance
  5. Compare cylinder balance and misfire counts; swap injectors if needed to see if the fault follows
  6. Pull the cylinder 6 spark plug: black sooty deposits point to a rich condition
  7. Check the air filter and intake path for restrictions
  8. Run a compression test and inspect the cylinder if fuel and electrical checks pass

Common fixes

  • Clean or replace the cylinder 6 fuel injector
  • Replace the fuel pressure regulator or fix the cause of high pressure
  • Replace a faulty MAF, MAP or oxygen sensor
  • Repair the injector wiring or connector
  • Replace a fouled spark plug and a clogged air filter
  • Repair the mechanical fault in the cylinder

Questions and answers

What does P02AF mean?

The ECU has cut fuel to cylinder 6 as far as it can and the mixture is still rich. The most common causes are the injector on that cylinder, fuel pressure or an air sensor.

Can I drive with code P02AF?

For a short while, yes, but a rich mixture can harm the catalytic converter and engine oil. If the engine misfires or the light flashes, stop driving and have it diagnosed.

Could a vacuum leak cause P02AF?

Usually not. A vacuum leak makes the mixture lean and sets a maximum-limit trim code instead. For P02AF, start with the injector, fuel pressure and sensors.

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.