P02C7: Cylinder 12 - Fuel Trim at Min Limit

What it means

The control module has reached the minimum fuel-trim correction for cylinder 12. This indicates a cylinder-specific mixture correction limit; the code alone does not identify the underlying cause.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Cylinder 12's fuel trim is the module's adjustment to the fuel delivered for that cylinder. The module monitors whether that adjustment can keep the cylinder's mixture within its control range. P02C7 sets when the correction reaches its minimum in the direction of reducing fuel, which can happen with excess fuel or a misleading mixture signal.

Common causes

Most likely first.

1. Cylinder 12 mixture control requiring maximum correction toward less fuel
2. Cylinder 12 injector leaking or over-delivering
3. Excessive fuel pressure
4. Cylinder 12 air-fuel measurement or wiring fault

Symptoms

• Check-engine light on
• Rough idle or misfire
• Poor fuel economy
• Fuel smell or dark exhaust smoke

How to diagnose it

1. Save the freeze-frame data and compare cylinder 12's fuel-trim and misfire readings with other cylinders to see when the correction bottoms out.
2. Check for fuel odor, dark exhaust, or a wet cylinder 12 spark plug, which can support an over-fueling diagnosis.
3. Inspect cylinder 12's injector, seal, connector, and wiring for leakage, damage, or poor contact.
4. Compare cylinder 12 injector operation with other cylinders and check mixture-sensor data for implausible readings or wiring faults.
5. Measure fuel pressure and cylinder 12 injector leakage or delivery against the manufacturer's specification.

Common fixes

• Repair a loose, damaged, or leaking cylinder 12 injector seal.
• Repair a fault in the cylinder 12 injector wiring or control circuit.
• Replace a cylinder 12 injector that leaks or over-delivers.
• Correct excessive fuel pressure if testing confirms it.
• Repair a mixture-sensor or related wiring fault when data and circuit checks identify it.

Can I keep driving?

Avoid extended driving if the exhaust smells of fuel, the engine misfires, or dark smoke is present; excess fuel can damage the catalytic converter and dilute engine oil. If the check-engine light flashes, stop driving when safe.