Cylinder 8 Injection Timing
What it means
P021B means the ECM has detected that the fuel injection timing for cylinder 8 is incorrect — fuel isn't being injected at the right moment for that cylinder. It's most common on direct-injection and diesel engines and usually traces to the injector itself, its wiring, or fuel-pressure and timing-reference problems. The result is rough running and reduced power from cylinder 8; a hard misfire can harm the catalytic converter, so it's worth prompt diagnosis.
Can I keep driving? Drivable but not ideal — cylinder 8 combustion is off, so expect rough running and reduced power; a hard misfire can harm the catalyst, so address it soon.
Common symptoms
What you'll notice
- Check-engine light on
- Rough running or misfire-like shake from cylinder 8
- Reduced power and hesitation
- Possible knock, noise, or extra smoke (diesel)
- Increased emissions
Common causes
Most likely first
- Faulty or worn fuel injector on cylinder 8Likely
- Injector wiring or connector fault affecting timingCommon
- Low or erratic fuel-rail pressureCommon
- Crankshaft/camshaft position sensor fault skewing the timing referenceLess often
- Failed ECM/PCM (rare)Less often
How to diagnose & fix
Work through it in order
- Read injector balance/correction and fuel-rail pressure data in live view to see how far cylinder 8 is off.
- Test fuel-rail pressure against spec — low or unstable pressure upsets injection timing.
- Inspect the cylinder 8 injector connector and wiring for damage or corrosion.
- Check the crank and cam position sensor signals for dropouts.
- Test or replace the injector as needed, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P021B?+
Can I just clear P021B?+
Related codes
Often seen with P021B
Read & clear P021B yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.