What does code P1231 mean?

Q: What does code P1231 mean?

Injector Circuit Cylinder 4 Intermittent. P1231 is a GM-specific code indicating that the engine control module (ECM) has detected an intermittent fault in the electrical circuit for cylinder 4's fuel injector. The ECM monitors injector current and voltage; when the signal drops out or spikes erratically, it flags the circuit as intermittent rather than a hard failure.

DTC codes / GM codes / P1231

P1231 · GMInjector Circuit Cylinder 4 Intermittent

P1231 is a GM-specific code indicating that the engine control module (ECM) has detected an intermittent fault in the electrical circuit for cylinder 4's fuel injector. The ECM monitors injector current and voltage; when the signal drops out or spikes erratically, it flags the circuit as intermittent rather than a hard failure.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.