For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

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 retarding the 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.

### Conditions for Running the DTC

• | The engine is running.

• | The DTCs run continuously once the above condition is met.

### Conditions for Setting the DTC

The ECM detects an invalid signal from the TCM for greater than 1 second.

### Action Taken When the DTC Sets

DTC P2544 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P2544 is a Type B DTC.

### Diagnostic Aids

• | This DTC may set due to low system voltage. Ensure the battery is completely charged. Refer to Battery Inspection/Test.

• | A fault in the serial data circuit will not cause DTC P2544 to set by itself. If a serial data circuit fault occurs, other DTCs will set before DTC P2544.

### Reference Information

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

### Circuit/System Verification

1. Ignition ON, observe the engine and transmission DTC information with a scan tool. Verify there are no UXXXX DTCs set.

⇒ | If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Observe the Freeze Frame/Failure Records with a scan tool.
3. Clear the DTCs with a scan tool.
4. Ignition OFF for 30 seconds.
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

⇒ | If DTC P2544 failed this ignition, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis of the TCM DTCs.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.