Powertrain, generic · Fuel and air metering (injector circuit)

P02C9 Cylinder 12 - Injector Leaking

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

These codes belong to an individual-cylinder fuel correction: a diesel's cylinder balance control measures each cylinder's crankshaft acceleration and adjusts its injection quantity; on petrol engines a cylinder-selective mixture control does the same. CARB requires the system to report when such a correction has used up its range or one cylinder causes an imbalance. P02C9 means the module detects fuel entering cylinder 12 outside the injection pulse – the injector is leaking or dripping. A BMW patent identifies such a leak by the fact that it persists with the injector switched off. A leaking diesel injector can dilute the oil or damage the piston, so act promptly. Cylinder 12 only exists on engines with twelve or more cylinders. GM and Ford use other codes for this (P0263 ff, P219A ff); no manufacturer document describing this code with thresholds was found, so the description follows CARB and published patents.

Likely causes

Nozzle seat or needle of the cylinder 12 injector leaking
Deposits keeping the needle from closing fully
Rail pressure too high
Wrong or wrongly coded injector

Symptoms

  • Check engine light on
  • Rough idle, vibration
  • Smoke, fuel smell, knocking

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–900
Time1–4 h

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

Parts involved

fuel injector cylinder 12crankshaft position sensorengine control module

Related codes

P02C6P02C7P02C8P0296P232DP0172

References: law.cornell.edu, patents.google.com, patents.google.com.