Transmission Diagnosis

DTC P0602
Circuit Description
A normal function of the transmission control module (TCM) is to perform an internal test that verifies the security of the diagnostic and control calibration programming. The programming must contain security codes that enable a software lock to engage. The software lock is designed to prevent unauthorized changes to the diagnostics or control calibrations. The software lock utility is processed independently from the diagnostic and control calibration software and contains application specific data. The software lock data is entered into the TCM during the final assembly of the vehicle.
When the security codes from the diagnostic and shift calibration software fail to engage the software lock, the TCM sets DTC P0602. DTC P0602 is a type A DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0602 Transmission Control Module (TCM) Not Programmed

Conditions for Running The DTC
The ignition is ON.

Conditions for Setting The DTC
The TCM detects an unlocked calibration memory range.

Action Taken When the DTC Sets
^ The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
^ The TCM commands maximum line pressure.
^ The TCM freezes transmission adaptive functions.
^ The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
^ The TCM stores DTC P0602 in TCM history.

Conditions for Clearing the MIL/DTC
^ The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the MIL/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
^ The TCM cancels the default actions when the ignition switch is OFF long enough in order to power down the TCM.

Diagnostic Aids
DTC P0602 may set as a result of TCM reprogramming.

Test Description





The number below refers to the step number on the diagnostic table.
3. This step eliminates the TCM software as a possible cause of the DTC. If the DTC continues to set after reprogramming, the fault is in the TCM hardware.