P1640

Circuit Description
Output Driver Modules (ODMs) are used by the power-train control module (PCM)/engine control module (ECM) to turn on the current driven devices that are needed to control various engine functions. The ODM is capable of controlling up to 7 separate outputs by applying ground to the device which the PCM/ECM is commanding ON. ODMs are capable of diagnosing each output circuit individually. This Diagnostic Trouble Code (DTC) detects a short to ground or open circuit and short to battery for the 7 low-side output devices of the ODM.

Since A/C is an option, NO A/C will cause the A/C clutch relay output to always fault. If a fault is seen on the A/C clutch relay output, it will not be logged as a fault until the A/C request input interrupts a high voltage, indicating that A/C has been installed.

Conditions for Setting the DTC
- Ignition ON.
- Ignition voltage is greater than or equal to 10 volts.
- Engine run time is greater than or equal to 5 seconds.
- DTC P1618 not set.

Action Taken When the DTC Sets
- The PCM/ECM will illuminate the Malfunction Indicator Lamp (MIL).
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffer.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC P1640 will clear after 40 consecutive warm-up cycles occur without a fault.
- The DTC P1640 can be cleared with a scan tool.

Diagnostic Aids
Check for the following conditions:
- Poor connection at the PCM/ECM - Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- Damaged harness - Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM/ECM, turn the ignition ON and observe a voltmeter connected to the MIL driver circuit at the PCM/ECM harness connector while moving connectors and wiring harnesses related to the MIL. A change in voltage will indicate the location of the fault.
- Poor connection at component - Examine for damaged connectors, unplugged connectors or damaged terminals at the various ODM controlled components.

The following PCM/ECM terminals are controlled by the ODM:
- C4 - Ignition Control (IC) A
- D5 - Ignition Control (IC) B
- A15 - Evaporative Emission (EVAP) Canister Purge Control
- C13 - Low Speed Cooling Fan Relay
- C12 - High Speed Cooling Fan Relay
- B14 - A/C Clutch Output

Steps 1 - 10:

Steps 11 - 16:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
3. Normally, ignition feed voltage is present on the output driver circuit with the PCM/ECM disconnected and the ignition turned ON.
4. Checks for a shorted component or a short B+ on the output driver circuit. Either condition would result in a measured current of over 1.5 amps. Also checks for a component that is going open while being operated, resulting in a measured current of 0 amps.
5. Checks for a fault component.
14. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.