GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P2544

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 Descriptor

DTC P2544: Transmission Torque Request Circuit

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 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.

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
    • DTC P2544 is a Type B DTC.
    • 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
    • DTC P2544 is a Type B DTC.
    • The ECM turns OFF the malfunction indicator lamp (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.

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 . Verify charging system is operating correctly. Refer to Charging System Test . Verify there is no parasitic drain on the battery. Refer to Battery Electrical Drain/Parasitic Load Test .

Reference Information

Schematic References

    •  Engine Controls Schematics
    •  Power Distribution Schematics
    •  Ground Distribution Schematics

Connector End View Reference

    •  Electrical Center Identification Views
    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Battery Inspection/Test
    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Troubleshooting with a Test Lamp
    •  Probing Electrical Connectors

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Verification

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. Using the DTC Descriptor and Diagnostic Aids determine which module is not communicating.
  2. Ignition OFF, disconnect the harness connector at the module that is not communicating.
  3. Test for less than 0.5 ohm of resistance between each ground circuit of the module that is not communicating and ground.
    4. ⇒If greater than 0.5 ohm, repair the open/high resistance in the ground circuit.
  4. Test for battery voltage between each battery positive voltage circuit of the module that is not communicating and ground.
    5. ⇒If less than battery voltage, repair the short to ground or open/high resistance in the battery positive voltage circuit.
  5. Ignition ON, test for battery voltage between each ignition circuit of the module that is not communicating and ground.
    6. ⇒If less than battery voltage, repair the short to ground or open/high resistance in the ignition circuit.
  6. Ignition OFF, disconnect the harness connector at the module that reported the no communication DTC.
  7. Ignition OFF, test for less than 0.5 ohm of resistance in each serial data circuit between the module that is not communicating and the module that reported the DTC.
    8. ⇒If greater than 0.5 ohm, repair the open/high resistance in the serial data circuit.
  8. If all tests normal, replace the module that is not communicating.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM or TCM replacement, programming, and setup