Powertrain, generic (extended)

P21C1 Cold Start Cylinder 12 Injection Timing

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Injector of cylinder 12 with deposits or worn needle
Damaged wiring at the end of the cylinder bank (injector 12)
Cold-start calibration of the engine module out of date

Symptoms

  • Check engine light after cold starts
  • Hardly any drivability change, at most a slightly uneven cold idle

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€250–3,000
Time2–8 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel injectorinjector wiringengine control module

Related codes

P21C0P021FP0212P0312P05EC

References: law.cornell.edu, en.wikipedia.org, en.wikipedia.org, en.wikipedia.org.