P021F
Cylinder 12 Injection Timing
Fuel injection (diesel)
Generic OBD-II
High
What it means
P021F means the engine controller has detected that fuel injection timing for cylinder 12 is off from what it commands. Injection timing that's early or late makes that cylinder burn poorly, so the engine runs rough, loses power, and may be harder to start. It usually points to the injector, the crank/cam timing signal, or its wiring.
High
Can I keep driving? You can usually drive short distances, but expect rough running and reduced power — have it looked at promptly to avoid stressing the engine.
Common symptoms
What you'll notice
- Check-engine light on
- Rough running or a noticeable miss from one cylinder
- Reduced power and hesitation
- Hard starting, and possibly extra exhaust smoke on a diesel
Common causes
Most likely first
- Faulty or contaminated fuel injector on cylinder 12Likely
- Crankshaft or camshaft position sensor giving an inaccurate timing referenceCommon
- Damaged wiring or connector in the injector/timing control circuitCommon
- Low or inconsistent fuel pressure affecting injection timingLess often
- Failed powertrain control module (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for companion injector or crank/cam sensor codes to narrow it down.
- Inspect the cylinder 12 injector wiring and connector for damage or corrosion.
- Test crankshaft and camshaft position sensor signals — a bad timing reference is a common trigger.
- Check fuel pressure and injector operation; substitute or bench-test the injector if suspect.
- If everything else checks out, have the PCM evaluated. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P021F?+
For short trips, usually — but the engine will run rough and down on power. Fix it soon to avoid further wear.
Can I just clear P021F?+
You can, but it will come back until the injector, timing signal, or wiring problem on cylinder 12 is repaired.
Related codes
Often seen with P021F
Read & clear P021F yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX