What Does P02C9 Mean?
The ECM has detected that the fuel injector on cylinder 12 is leaking, delivering more fuel than commanded. The PCM identifies this through negative individual fuel trim values that have reached their correction limit, or by detecting abnormal fuel pressure decay with the injector commanded off. The driver may notice a rich exhaust smell, rough idle, black exhaust smoke, or oil dilution over time.
Common Causes
40%
Worn or damaged injector pintle/seat allowing fuel to drip when closed
25%
Cracked or deteriorated injector O-ring seals causing external fuel leak
15%
Carbon buildup preventing the injector valve from fully seating closed
12%
Electrical fault holding the injector solenoid partially energized
8%
Excessive fuel system pressure forcing fuel past the injector seal
Diagnostic Steps
1
Monitor cylinder 12 individual fuel trim — a large negative trim (e.g., -20% or more) confirms the ECM is compensating for excess fuel delivery.
2
Perform a fuel rail pressure decay test: key on/engine off, pressurize the fuel rail, and monitor for abnormal pressure drop indicating a leaking injector.
3
Remove and inspect the cylinder 12 spark plug — heavy black soot or wet fuel fouling confirms that cylinder is running rich from injector leakage.
4
With the injector removed, apply regulated fuel pressure and observe the injector tip — any dripping with the injector de-energized confirms an internal leak. Maximum allowable leakage is typically 1 drop per minute.
5
Check the injector O-rings and fuel rail seating surface for cracks, hardening, or fuel residue indicating an external seal leak.
Estimated Repair Cost
$200 - $900
Parts + labor, varies by vehicle and location
The ECM has detected that the fuel injector on cylinder 12 is leaking, delivering more fuel than commanded. The PCM identifies this through negative individual fuel trim values that have reached their correction limit, or by detecting abnormal fuel pressure decay with the injector commanded off. The...
The most common cause of P02C9 (Cylinder 12 - Injector Leaking) is: Worn or damaged injector pintle/seat allowing fuel to drip when closed
Typical repair costs for P02C9 range from $200 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A leaking injector is a moderate fire risk if the leak is external, and will cause catalyst damage and oil dilution if internal. Do not ignore this code — have it repaired within a few days. If you smell raw fuel, stop driving immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02C9 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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