Circuit Description
A normal function of the transmission control module (TCM) programming is to perform a test that verifies the internal power control relay is functioning correctly.
When the TCM identifies that the power control relay is not functioning properly, then DTC P1600 will set. DTC P1600 is a type B DTC.
Conditions for Running the DTC
The ignition is ON.
The TCM power control relay is closed.
Condition for Setting the DTC
The TCM identifies that the power control relay is not functioning properly.
Action Taken When the DTC Sets
| • | The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL. |
| • | The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM. |
| • | The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts). |
Conditions For Clearing the MIL/DTC
| • | The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request. |
| • | A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic. |
| • | The scan tool clears the MIL/DTC. |
| • | The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM. |
Diagnostic Aids
Observe the power relay status on the scan tool. The power relay status should display On.
Test Description
The number below refer to the step number on the Diagnostic Table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission ? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission | |
Important: Record the Failure Records before clearing the DTCs. Using the Clear Info function erases the Failure Records from the ECM and the TCM. Does the Scan Tool power relay status change to reflect the commanded change when the power relay is commanded ON and OFF? | -- | Go to Diagnostic Aids | ||
3 |
Caution: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Refer to Disabling the SIR System. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs. Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | -- | |
4 | Perform the following procedure in order to verify the repair:
Did DTC P1600 reset? | System OK |
