Fuel and air

P02BF — Cylinder 10 Fuel Trim at Minimum Limit

Severity: medium Drive with care, to a shop

What P02BF means

The engine control module constantly adjusts fuel delivery to each cylinder based on air/fuel sensor feedback. P02BF means the correction for cylinder 10 has hit its lower limit: the module is already cutting as much fuel as it can, yet the mixture is still too rich. The usual culprit is the injector for that cylinder or its control circuit.

Symptoms

  • Check engine light on
  • Rough idle or vibration
  • Higher fuel consumption
  • Fuel smell from the exhaust or black smoke
  • Hesitation or loss of power
  • Possible misfire on cylinder 10

Possible causes

  1. Leaking or stuck-open fuel injector on cylinder 10
  2. Injector circuit fault (wiring, connector or short)
  3. Excessive fuel pressure from a bad regulator or restricted return line
  4. Dirty or faulty air/fuel ratio sensor on the affected bank
  5. Fuel in the oil or a bad spark plug on cylinder 10 skewing readings
  6. ECM fault (rare)

How to diagnose

  1. Scan for all codes and freeze-frame data and note any other fuel trim or misfire codes
  2. Compare per-cylinder and per-bank fuel trim values on a scan tool
  3. Inspect the cylinder 10 injector harness and connector for damage, corrosion and chafing
  4. Measure injector resistance and check the drive signal with a scope or noid light
  5. Test fuel pressure and check how well it holds after shutdown
  6. Swap the injector with a neighboring cylinder and see whether the fault follows it
  7. Check the air/fuel sensors and their wiring
  8. Smell the oil for fuel and inspect the cylinder 10 spark plug

Common fixes

  • Replace the leaking cylinder 10 injector
  • Repair the injector wiring or connector
  • Replace the fuel pressure regulator or fix the cause of high pressure
  • Replace a faulty air/fuel ratio sensor
  • Clear codes, reset fuel adaptations and change the oil if it is contaminated with fuel

Questions and answers

What does P02BF mean in simple terms?

The ECM thinks cylinder 10 is getting too much fuel and has already reduced delivery as far as it can. With no room left to correct, it stored the code.

Can I drive with code P02BF?

Only briefly, for example to a repair shop. Running rich for long can foul the oil and damage the catalytic converter.

Why does the code point to cylinder 10 specifically?

Codes like this appear on engines with many cylinders, such as V10 or V12 engines. The module sees the deviation in just one cylinder, so that cylinder's injector and circuit are the first suspects.

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.