Fuel and air

P02B6 — Cylinder 8 Fuel Trim at Maximum Limit

Severity: medium Drive with care, to a shop

What P02B6 means

The engine control module monitors the air/fuel mixture and adjusts injector timing for each cylinder. P02B6 means the correction for cylinder 8 has reached its limit and can no longer compensate. The mixture in that cylinder is usually too lean or too rich because of an injector, an air leak or a fuel delivery problem.

Symptoms

  • Check Engine light on
  • Rough idle
  • Misfire or hesitation when accelerating
  • Reduced power
  • Worse fuel economy
  • Higher exhaust emissions

Possible causes

  1. Clogged, leaking or failing fuel injector on cylinder 8
  2. Intake air leak near cylinder 8 (manifold gasket, hoses, vacuum lines)
  3. Low fuel pressure (pump, filter or pressure regulator)
  4. Oxygen sensor or mass airflow sensor giving wrong readings
  5. Worn spark plug or weak ignition coil on cylinder 8
  6. Damaged wiring or a poor connection at the injector connector
  7. Exhaust leak ahead of the oxygen sensor

How to diagnose

  1. Scan for codes and freeze frame data, and look for related misfire or fuel mixture codes
  2. Check short-term and long-term fuel trims at idle and under load
  3. Inspect the intake system and vacuum hoses, and smoke test for air leaks
  4. Measure fuel pressure and compare it with specifications
  5. Inspect the cylinder 8 injector connector and wiring, and measure injector resistance
  6. Compare cylinder balance and misfire counts, and swap the coil or plug to see if the problem follows
  7. Check mass airflow and oxygen sensor readings
  8. Inspect the exhaust for leaks

Common fixes

  • Clean or replace the cylinder 8 fuel injector
  • Repair intake leaks and replace the manifold gasket or hoses
  • Replace a faulty mass airflow or oxygen sensor
  • Restore fuel delivery by replacing the filter, pump or pressure regulator
  • Repair wiring or connectors, and replace the spark plug or coil if faulty

Questions and answers

What does P02B6 mean?

It means the engine computer has used up its fuel trim adjustment range for cylinder 8. It can no longer correct the mixture there, usually due to an injector, air leak or fuel supply problem.

Can I drive with code P02B6?

Only for a short time and without heavy loads. Running lean or misfiring for long can overheat the cylinder and damage the catalytic converter.

What should I check first for P02B6?

Start with the fuel trim data and look for air leaks near cylinder 8. Then check the injector, its connector and the 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.