Fuel and air

P02B9 — Cylinder 8 Fuel Injector Leaking

Severity: medium Drive with care, to a shop

What P02B9 means

The engine control unit has detected signs that the cylinder 8 fuel injector is leaking, letting fuel into the cylinder when it should be closed. This usually shows up as fuel trim deviations and rough running on that cylinder. Normally the injector opens only when the ECU commands it and seals tightly while rail pressure is held.

Symptoms

  • Check Engine light on
  • Rough idle or misfire on cylinder 8
  • Hesitation and weak acceleration
  • Higher fuel consumption
  • Fuel smell or smoky exhaust
  • Long cranking on a hot restart

Possible causes

  1. Leaking or sticking cylinder 8 injector
  2. Contamination keeping the injector from seating
  3. Worn or damaged injector seals or O-rings
  4. Poor connection, open, or short in the injector wiring or connector
  5. Incorrect fuel rail pressure
  6. Air leak or other cause of mixture error
  7. Faulty injector driver in the ECU (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and look for a cylinder 8 misfire code
  2. Check short- and long-term fuel trims on the bank with cylinder 8
  3. Inspect the injector 8 connector and wiring for damage or poor contact
  4. Measure injector coil resistance and compare it with the other injectors
  5. Test fuel pressure and how well it holds after shutoff
  6. Compare cylinder contribution, or swap injectors and see if the fault follows
  7. Pull the cylinder 8 spark plug and look for signs of a rich condition
  8. Inspect the intake and exhaust for leaks

Common fixes

  • Replace the leaking cylinder 8 injector along with new seals
  • Repair the injector wiring or connector
  • Clean and bench-test the injector if contamination is the cause
  • Fix fuel supply problems or air leaks
  • Reflash or replace the ECU only after confirming it is faulty

Questions and answers

What does P02B9 mean?

The ECU found signs of fuel leaking through the cylinder 8 injector. The injector or its seals are the most common cause, with wiring less often.

Can I drive with P02B9?

Only briefly, to reach a shop. Driving long with misfires can damage the catalytic converter and wash oil from the cylinder wall.

Will injector cleaning fix it?

If the cause is deposits, cleaning may help. If the injector is worn or mechanically damaged, it needs to be replaced.

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.