Intermittent Misfires With P0300 - keywords circuit coil DTC ECM injector intermittent LY7 MIL misfire P0300 SES

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may complain about the SES light on along with the Traction Control light being on. They will also complain about the vehicle running rough all the time or intermittently

If normal diagnostics does not find concern the check the engine wiring harness. Previous cases have indicated the the four circuits from the ECM to the coil and the two circuits to the injector may be broken inside the insulation. Try to isolate to one cylinder using the misfire data and check this circuit for intermittent opens.

Helpful Hint: Move the wiring harness at the ignition coil connector while the vehicle is running to see if the engine misfire goes away.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.