Output Driver 1

The Powertrain Control Module (PCM) contains an Output Driver Module (ODM) which is used to control up to seven different outputs. The ODM controls these components individually by completing the ground circuit when the PCM commands them On. ODM 1 is used to control the following components: cooling fan control module, EVAP vent solenoid, EVAP purge solenoid, TCC solenoid and A/C relay.

Each of the circuits controlled by the ODM has a feedback circuit. The PCM can compare expected voltage (determined by what the PCM is commanding) and actual voltage on its feedback. For example, if a solenoid is shorted, having very low or zero resistance, or if the control side of the circuit is shorted to voltage, it would allow too much current to flow into the PCM. The ODM senses this and that individual output is turned Off. The ODM will continue to try and turn the output On, until the short is removed or the output is no longer being commanded On (e.g. A/C is no longer being requested). In this example, the PCM is commanding the output On so it expects to see zero volts on the feedback. however, the ODM cannot keep the circuit grounded due to the overload of current, therefore the feedback voltage will be near battery voltage. This will set DTC P1640.

IMPORTANT: The DTC will not set until the PCM commands the output On (grounded), because that is when the expected voltage does not match the feedback voltage.

By examining the failure record for DTC P1640 you can determine which of the outputs caused the DTC to set. There are several parameters in the failure record which need to be examined. For each output there are two parameters. One reports an Open/Short to GND and the other is Short To Volts. Any feedback parameter which indicates "Yes" has/had detected a fault.

Use the following references to determine which of the charts to use for diagnosis of DTC P1640.

DTC PARAMETERS
DTC P1640 will set if feedback voltage does not agree with expected voltage (based on commanded state of output).




DIAGNOSTIC AIDS
The Sean tool can be used to command each of the outputs On or Off to help in finding an intermittent condition.
^ Using Scan tool, review failure record for DTC P1640.
^ Note which feedbacks indicate a Yes.
^ Refer to appropriate chart.

NOTE: If A/C relay, EVAP vent and EVAP purge Open/short to GND are all Yes then inspect IGN 3 fuse to see is blown. If blown, repair short to ground in ignition feed circuit or components.