P21C1 code meaning
Cold Start Cylinder 12 Injection Timing
Powertrain system Generic code P21xx codes Check engine light
What P21C1 means
Cylinder 12 is the last cylinder of V12 and W12 engines. Direct-injection V12 include Ferrari's F140 family (FF, F12berlinetta, 812 Superfast) and BMW's N74; among W engines there is the 6.3-litre W12 FSI. P21C1 reports that during the cold-start heating phase the injection timing of cylinder 12 deviated from its target. The code closes the series P21B6–P21C1, which exists because CARB requires cold-start faults to be kept apart from normal ones; the following code, P21C2, already belongs to the SCR reductant heater. No manufacturer publishes use of P21C1. Practical cross-checks: P021F (timing, warm engine), P0212 (injector circuit) and P0312 (misfire). Repairs on these engines are workshop jobs.
P21C1 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor2 to 8 hours
- Clears after repairAfter a drive cycle
Symptoms of P21C1
- Check engine light after cold starts
- Hardly any drivability change, at most a slightly uneven cold idle
Common causes of P21C1
- Most likelyInjector of cylinder 12 with deposits or worn needle
- PossibleDamaged wiring at the end of the cylinder bank (injector 12)
- Less likelyCold-start calibration of the engine module out of date
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injectorInjector wiringEngine control module
What each part of P21C1 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| C1 | The exact fault in that area. |
What to do next
- Note P21C1 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P21C1
What does P21C1 mean?
P21C1 means "Cold Start Cylinder 12 Injection Timing". Cylinder 12 is the last cylinder of V12 and W12 engines. It is a generic code, so it means the same on every make.
Is it safe to drive with P21C1?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P21C1 fail an emissions test?
Yes, it can. P21C1 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P21C1 to fix?
Difficulty: workshop only. A typical repair takes 2 to 8 hours of work. This is a job for a workshop.
Will P21C1 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.