Fuel and air

P02C7 — Cylinder 12 Fuel Trim at Minimum Limit

Severity: medium Drive with care, to a shop

What P02C7 means

P02C7 means the engine control module has reduced fuel delivery to cylinder 12 as far as it is allowed, yet the mixture is still too rich. The ECM constantly adjusts each injector's pulse using oxygen sensor and airflow data. When the correction range is used up, it sets this code. It appears on multi-cylinder engines (such as V12s) that track fuel trim per cylinder.

Symptoms

  • Check Engine light on
  • Rough or unstable idle
  • Reduced power and sluggish acceleration
  • Higher fuel consumption
  • Fuel smell or black smoke from the exhaust
  • Misfire or hesitation under acceleration

Possible causes

  1. Leaking or stuck-open fuel injector on cylinder 12
  2. Injector circuit fault: open circuit, poor connector contact or damaged wiring
  3. Faulty readings from an oxygen sensor or MAF/MAP sensor
  4. Excessive fuel pressure from a failing pressure regulator
  5. Dirty or aging sensor causing the ECM to misjudge the mixture
  6. Faulty ECM (rare)

How to diagnose

  1. Scan all codes and freeze-frame data and look for other mixture or misfire codes.
  2. View short-term and long-term fuel trims for both banks and, if supported, per cylinder.
  3. Inspect the cylinder 12 injector wiring and connector for corrosion, damage or a loose fit.
  4. Measure injector coil resistance and check the drive signal with a scope or noid light.
  5. Compare cylinder balance and run an injector test with the scan tool.
  6. Measure fuel pressure and confirm it is in spec and holds after shutoff.
  7. Check oxygen and MAF/MAP sensor readings against engine conditions.
  8. Pull the cylinder 12 spark plug; sooty deposits point to a rich condition.

Common fixes

  • Replace or professionally clean the cylinder 12 injector
  • Repair the injector wiring or connector
  • Replace a faulty oxygen or airflow sensor
  • Replace the fuel pressure regulator if pressure is too high
  • Clear adaptations and codes, then verify fuel trims on a warm engine

Questions and answers

What does P02C7 mean?

The ECM has cut fuel to cylinder 12 to its minimum, but the mixture is still too rich. The usual suspects are the injector, its wiring or bad sensor readings.

Can I drive with P02C7?

For a short time, yes, if the engine runs smoothly. A rich mixture raises fuel use and can damage the catalytic converter, so diagnose it soon.

Will clearing the code fix it?

Only temporarily. If the cause remains, the ECM will set the code again, usually within a few drives.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.