DTC P1640: Pcm Output Circuit: Description

The PCM contains an output driver module (ODM) which controls 7?circuits: A/C relay, air pump relay, EVAP purge solenoid, EVAP vent solenoid, fan control?1, fan control?2, and TCC solenoid. The ODM controls each of these circuits independently by controlling the circuit ground. The ODM monitors the voltage level at each of the 6?circuits into the PCM when the device is being commanded ON or OFF. When the device is commanded OFF, the circuit is not grounded, the voltage level at the PCM should be high (ignition voltage). When the device is commanded ON, the circuit is grounded, the voltage level at the PCM should be low. Each of the 7?drivers in the ODM contains a feedback circuit used to determine if a particular circuit failed, which can be read on the scan tool. DTC?P1640 sets when any one of the 7?feedback voltages is low when that device is turned OFF or when any one of the 7?feedback voltages is high when that device is turned ON when the engine is running.