4T45-E - Automatic Transmission

DTC P2544

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC P2544
- Transmission Torque Request Circuit

Circuit/System 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 delaying 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 (CAN). Two circuits are used to communicate CAN data between the ECM and TCM. A fault in the CAN will not cause DTC P2544 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P2544.

Conditions for Running the DTC

* No other CAN errors are present.
* The engine is running for 5 seconds and not in fuel cut-off.

Conditions for Setting the DTC

The ECM notifies the TCM that a torque reduction request has failed for 1 second.

Action Taken When the DTC Sets

* DTC P2544 is a Type B DTC.
* The TCM commands maximum line pressure.
* The TCM freezes transmission adaptive functions.

Conditions for Clearing the DTC

DTC P2544 is a Type B DTC.

Diagnostic Aids

It is possible for this DTC to set due to a stack-up or misalignment issue, where no electrical fault is present. Ensure the gear shift selector cable is properly adjusted and there are no service bulletins that address this concern before replacing parts.

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (4T45-E - Automatic Transmission)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Data Link Communications Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Start the engine; observe the DTC information with a scan tool. CAN DTCs should not set.
2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Ignition ON, attempt to establish communication with the ECM with a scan tool.

• If no communication with the ECM, refer to Control Module References (Programming and Relearning) for further diagnosis.

2. Ignition OFF, disconnect the harness connector of the ECM.
3. Ignition ON, verify that 1.5-3.4 volts is available between the CAN serial data low and the CAN serial data high circuits.

• If the voltage is not within the specified range, replace the ECM.

4. Ignition OFF, test the CAN communication circuits between the ECM and the TCM for an open, short to ground, or a short to voltage.
5. If the circuits/connections test OK, replace the TCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the repair.

Control Module References (Programming and Relearning) for TCM replacement, setup, and programming