Circuit Description
The engine control module (ECM) contains an output driver module (ODM) that controls four devices:
| • | The A/C relay |
| • | The main relay |
| • | The evaporative emission (EVAP) vent solenoid |
| • | The EVAP purge solenoid |
The ODM provides grounded output control of the above devices through separate control circuits. The ODM monitors the voltage level at each of the control circuits when the device is commanded ON or OFF. Each ODM output has an internal feedback circuit that connects to the ECM microprocessor. The ECM monitors voltage through the ignition 1 voltage circuit. Excessive voltage or current may cause damage to the ECM. If the ODM detects excessive current or voltage on an output control circuit, this DTC will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1640 Control Module Output A Circuit
Conditions for Running the DTC
DTC P1640 runs continuously when the ignition is ON.
Conditions for Setting the DTC
| • | The ODM has detected a voltage greater than 33 volts. |
| OR |
| • | Excessive current is detected on any circuit to the ODM. |
| • | The above condition is present for 6 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | A condition with the charging system may cause this DTC to set. Refer to Diagnostic Starting Point - Engine Electrical . |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Is DTC P0446, P0496, P0560, or P0563 set? | Go to Step 3 | |
3 | Observe the General Info - Output Data List with a scan tool. Do any parameters indicate a fault present? | Go to Step 4 | Go to Step 5 |
4 | Test for a short to voltage on the control circuit of the component that indicated a fault. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 | Replace the engine control module (ECM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC fail this ignition? | Go to Step 2 | Go to Step 7 |
7 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
