What Does P02C7 Mean?
The ECM has detected that the individual fuel trim correction for cylinder 12 has reached its minimum (maximum lean correction) limit. The PCM is subtracting as much fuel as possible from cylinder 12 but cannot lean it out enough, indicating the cylinder is running excessively rich. The driver may notice black smoke, a fuel smell, rough idle, or degraded fuel economy.
Common Causes
40%
Leaking fuel injector on cylinder 12 allowing excess fuel delivery when closed
20%
Faulty injector driver circuit holding injector open longer than commanded
18%
Oil or carbon fouled spark plug on cylinder 12 causing incomplete combustion
12%
Cylinder 12 exhaust valve not sealing properly causing O2 sensor misread
10%
Excessive fuel rail pressure from stuck-closed regulator
Diagnostic Steps
1
Monitor cylinder 12 individual fuel trim via live data — values near -25% or lower confirm the ECM is at its maximum fuel subtraction limit.
2
Remove and inspect the cylinder 12 spark plug for black soot or wet fuel fouling, which confirms rich combustion in that specific cylinder.
3
Perform an injector leak-down test by pressurizing the fuel rail with the engine off and monitoring for pressure drop; inspect cylinder 12 injector for dripping.
4
Measure injector resistance at cylinder 12 (typically 11-18 ohms) and compare to adjacent cylinders; check wiring for shorts that could hold the injector open.
5
Check fuel pressure at idle and snap-throttle — verify it is within manufacturer specification; excessively high pressure points to a regulator fault.
Estimated Repair Cost
$200 - $850
Parts + labor, varies by vehicle and location
The ECM has detected that the individual fuel trim correction for cylinder 12 has reached its minimum (maximum lean correction) limit. The PCM is subtracting as much fuel as possible from cylinder 12 but cannot lean it out enough, indicating the cylinder is running excessively rich. The driver may n...
The most common cause of P02C7 (Cylinder 12 - Fuel Trim at Min Limit) is: Leaking fuel injector on cylinder 12 allowing excess fuel delivery when closed
Typical repair costs for P02C7 range from $200 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven short distances, but a rich-running cylinder will foul spark plugs, contaminate catalytic converters, and dilute engine oil with fuel. Address within a few days to prevent catalyst and engine damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P02C7 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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