AF40-6 (MDK) - 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 Descriptors

DTC P2544
- Transmission Torque Request Signal Message Counter Incorrect

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 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 (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. When the TCM receives a torque reduction malfunction message from the ECM, then DTC P2544 will set.

Conditions for Running the DTC

* The ignition voltage is 10.2-15.5 V.

* The engine speed is running for 0.5 s.

* Communication is normal.

* 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 s.

Action Taken When the DTC Sets

* DTC P2544 is Type B DTC.

* The TCM commands maximum line pressure.

Conditions for Clearing the DTC

DTC P2544 is Type B DTC.

Diagnostic Aids

This diagnostic trouble code may set due to low system voltage. Ensure that the vehicle battery has passed a load test and is completely charged, refer to Battery Inspection/Test Battery Inspection/Test. Verify charging system is operating correctly, refer to Charging System Test (Without CZ2) Charging System Test (Without CZ2)Charging System Test (With CZ2) Charging System Test (With CZ2). Verify there is no parasitic drain on the battery, refer to Battery Electrical Drain/Parasitic Load Test Battery Electrical Drain/Parasitic Load Test.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics AF40-6 (MDK) - Automatic Transmission

Connector End View Reference

Component Connector End Views Sunshade - Left

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

Description and Operation

Transmission Component and System Description Transmission Component and System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Verify DTC U0100 and CAN DTCs not set.

• If DTC U0100 or CAN DTCs set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle

• If DTC U0100 or CAN DTCs not set

2. Operate the vehicle within the conditions for running the DTC. It may be helpful to operate the vehicle within the conditions identified from the Freeze Frame/Failure Records data.

3. Verify DTC P2544 is not set.

• If DTC P2544 is set
Refer to Circuit/System Testing

• If DTC P2544 is not set

4. All OK

Circuit/System Testing

1. Ignition ON.

2. Verify the ECM communication with a scan tool.

• If no communication with the ECM
Refer to Control Module References Control Module References for further diagnosis.

• If the communication with the ECM OK

3. Test or replace the K20 Engine Control Module.

4. Verify the DTC P2544 does not set while operating the vehicle under the Conditions for Running the DTC.

• If DTC P2544 is set

5. Test or replace the K71 Transmission Control Module.

• If DTC P2544 is not set

6. All OK

Repair Instructions

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

* Refer to Control Module References Control Module References for ECM or TCM, replacement, programming and setup.

* Perform the Transmission Adaptive Functions Transmission Adaptive Functions.