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 the controller area network (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, which is a type 'B' DTC.
Conditions for Running the DTC
| • | Ignition voltage is between 8.0 and 18.0 volts. |
| • | The engine speed is between 450 and 6,800 RPM more than 5 seconds. |
| • | No other CAN 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 drive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM disables the pressure control solenoid (PCS). This results in 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 MIL/DTC
| • | The ECM turns OFF the MIL after the sixth consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | Tech 2 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 to power down the TCM. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics For information on testing wiring faults, refer to Wiring Systems. | ||||
1 | Has the Diagnostic System Check - Automatic Transmission been completed? | -- | Go to Step 2 | |
2 |
Did you record any ECM DTCs? | -- | 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 |
Is the action complete? | -- | Go to Step 6 | -- |
6 | Perform the following operation to verify the repair.
Does the DTC reset? | -- | Go to Step 7 | Go to Step 2 |
7 | Using Tech 2, observe the stored information, capture info and DTC info. Does Tech 2 display any DTCs that you have not diagnosed? | -- | System OK | |
When all diagnosis and repairs are completed, clear all DTCs and verify correct operation. | ||||
