Fuel and air

P021F — Cylinder 12 Injection Timing Malfunction

Severity: medium Drive with care, to a shop

What P021F means

P021F is set when the engine control unit sees the injection timing for cylinder 12 fall outside the expected range. The module compares the injector command with the crankshaft and camshaft position signals, and logs the code when they disagree. The cause can be the injector, its wiring, a position sensor, a mechanical timing problem, or the control unit itself. It appears on 12-cylinder engines and some large diesels.

Symptoms

  • Check Engine light on
  • Rough idle or misfire
  • Reduced power and poor acceleration
  • Higher fuel consumption
  • Possible increased exhaust smoke
  • Hesitation or jerking under load

Possible causes

  1. Faulty or clogged cylinder 12 fuel injector
  2. Damaged wiring or poor connector contact in injector or sensor circuits
  3. Failing crankshaft or camshaft position sensor, or a bad signal
  4. Stretched or worn timing chain or belt, or shifted cam timing
  5. Low fuel pressure or supply problem
  6. Air leak skewing the air-fuel mixture
  7. PCM software or internal fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and look for related misfire or sensor codes
  2. Review fuel trims and mixture adaptation by bank
  3. Compare cylinder balance or misfire counts per cylinder
  4. Inspect the cylinder 12 injector connector and harness, and test injector resistance, power, and ground
  5. Check crankshaft and camshaft sensor signals with a scope
  6. Measure fuel pressure and verify supply
  7. Check the intake and exhaust for leaks
  8. Verify timing marks and inspect the drive for wear

Common fixes

  • Clean or replace the cylinder 12 injector
  • Repair wiring and connectors in the injector and sensor circuits
  • Replace a faulty crankshaft or camshaft position sensor
  • Correct cam timing and replace the chain, belt, or tensioners
  • Reflash or replace the PCM only after other causes are ruled out

Questions and answers

What does P021F mean?

The PCM found that fuel injection in cylinder 12 is not happening at the right moment. It usually traces back to the injector, wiring, position sensors, or mechanical timing.

Can I drive with code P021F?

Only a short distance, such as to a shop. If the engine misfires or loses power, stop driving to avoid damaging the catalytic converter and engine.

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.