Diagnostic Aids

If PCM is defective, verify that EVO solenoid diagnostic feedback circuit is not shorted to battery voltage. A short to voltage in this circuit will damage the internal resistor in the new PCM.

DTC may be set by loss of ignition when vehicle is still moving. This is a normal condition. Review malfunction history data to verify if failure was feedback low/high. Feedback high indicates a short to voltage in EVO control signal circuit. Feedback low indicates an open/short to ground in the circuit.

If DTC is not present but there is a steering effort complaint, diagnose steering system. If EVO solenoid is shorted or if the EVO solenoid circuits are shorted to each other, PCM will not provide output voltage on the EVO control signal circuit. Ignition must be cycled after a repair or DTC P1555 will reset.