Fuel and air

P02B2 — Cylinder 7 Fuel Trim at Maximum Limit

Severity: medium Drive with care, to a shop

What P02B2 means

The engine control unit monitors the air-fuel mixture and adjusts fuel delivery for each cylinder. P02B2 sets when the correction for cylinder 7 hits its maximum limit and can no longer compensate. This means the mixture in that cylinder is too lean or too rich.

Symptoms

  • Check Engine light on
  • Rough idle or vibration
  • Reduced power and sluggish acceleration
  • Hard or delayed starting
  • Poor fuel economy
  • Possible misfire in the cylinder
  • Increased emissions

Possible causes

  1. Clogged or faulty fuel injector on cylinder 7
  2. Vacuum or intake air leak near cylinder 7
  3. Faulty oxygen sensor
  4. Faulty MAF or MAP sensor
  5. Fuel supply problem such as low fuel pressure
  6. Wiring or connector fault at the injector
  7. Mechanical problem in cylinder 7, such as low compression, valve or piston ring wear

How to diagnose

  1. Scan all codes and freeze frame data, noting any misfire or other fuel trim codes
  2. Read short-term and long-term fuel trims at idle and under load
  3. Inspect intake hoses, manifold gaskets and seals, and look for vacuum leaks with a smoke test or spray test
  4. Check the cylinder 7 injector connector and wiring, and test resistance and the control signal
  5. Compare cylinder performance with an injector balance test or cylinder cutout
  6. Measure fuel pressure against specification
  7. Check MAF/MAP readings and oxygen sensor response
  8. If still unclear, run a compression or leak-down test on cylinder 7

Common fixes

  • Clean or replace the cylinder 7 fuel injector
  • Repair vacuum leaks: replace gaskets, hoses or seals
  • Replace the faulty MAF, MAP or oxygen sensor
  • Repair the injector wiring or connector
  • Fix confirmed mechanical problems in the cylinder, such as valves or piston rings

Questions and answers

What does P02B2 mean?

The ECU has run out of room to adjust fuel for cylinder 7, so the mixture there is too lean or too rich. The cause is usually the injector, an air leak or a sensor.

Can I drive with code P02B2?

A short trip to a shop is generally fine if the engine runs smoothly. If it misfires, stop driving, since the catalytic converter and engine can be damaged.

Where do I start diagnosing P02B2?

Check the fuel trims and look for an air leak near cylinder 7. Then test the injector and its wiring, fuel pressure and the air flow and oxygen 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.