Circuit Description
To improve shift feel, the transmission control module (TCM) may request that the engine control module (ECM) reduce engine torque during shift events. When such a request is received, the ECM responds by retarding the base ignition timing and notifying the TCM that the request has succeeded. If the ECM is unable to comply with the request, the ECM sends the TCM a message that the request has failed.
The torque reduction request is sent to the ECM through a communication network called GMLAN. Two circuits are used to communicate GMLAN data between the ECM and TCM. A fault in the GMLAN will not cause DTC P2544 to set by itself. If a GMLAN fault occurs, other DTCs will set before DTC P2544.
When the TCM receives a torque reduction failure message from the ECM, then DTC P2544 will set. DTC P2544 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2544 Transmission Torque Request Circuit
Conditions for Running the DTC
| • | The engine run time is greater than 5 seconds. |
| • | No other GMLAN errors are present. |
Conditions for Setting the DTC
The ECM notifies the TCM that a torque reduction request has failed for 2 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM turns power off to the PCS. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
| • | At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. |
| • | At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame. |
| • | The TCM stores DTC P2544 in TCM history. |
Conditions for Clearing the DTC
| • | The ECM turns OFF the MIL after the sixth consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non emission related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM. |
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
2 |
Important:
Did you record any ECM Failure Records? | -- | Go to Step 3 | |||||
3 |
Did DTC P2544 reset? | -- | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections | ||||
4 | Did any other DTCs set? | -- | Go to Step 5 | |||||
5 | Replace the TCM. Refer to Control Module References. Is the action complete? | -- | Go to Step 6 | -- | ||||
6 | Perform the following operation to verify the repair:
Has the test run and passed? | -- | Go to Step 7 | Go to Step 2 | ||||
7 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
