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 shift 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 diagnostic or shift calibrations. The software lock utility is processed independently from the diagnostic and shift calibration software and contains application specific data. This 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, which is a type 'A' DTC.
Conditions for Running the DTC
The ignition is switched ON.
Conditions for Setting the DTC
The TCM detects an unlocked calibration memory range (i.e. the flash memory has not been programmed).
Action Taken When the DTC Sets
| • | The TCM requests the Powertrain Interface Module (PIM) to illuminate the Check Powertrain Malfunction Indicator Lamp (MIL). |
| • | The TCM also turns off the pressure control solenoid (causing maximum line pressure). |
| • | The TCM turns off power to the shift solenoids. |
| • | The transmission will operate in fifth gear if the vehicle has successfully completed a 1-2 upshift in the current ignition cycle. If the vehicle has not completed a 1-2 upshift in the current ignition cycle, the transmission will operate in fourth gear. |
| • | 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 freezes the transmission adaptive learning function. |
| • | Powertrain braking is disabled (i.e. no coast down clutch operation). |
| • | The torque converter clutch is disabled. |
| • | The TCM stores DTC P0602 into TCM history. |
Conditions for Clearing the MIL/DTC
| • | The PIM turns off the Check Powertrain MIL after the sixth consecutive drive trip in which the TCM does not send a Check Powertrain MIL illumination request. |
| • | Tech 2 can clear the DTC. |
| • | The TCM clears the DTC from its memory (history DTC) if the vehicle completes 40 warm-up cycles without a non-emission related DTC occurring. |
| • | The TCM cancels the default actions when the ignition is off long enough to power down the TCM. |
Diagnostic Aids
DTC P0602 may set as a result of TCM programming.
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.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics For information on testing wiring faults, refer to Wiring Systems. | |||
1 | Has the Diagnostic System Check - Automatic Transmission been completed? | Go to Step 2 | |
2 |
Did DTC 0602 reset? | Go to Step 3 | Go to Diagnostic Aids |
3 | Perform the TCM programming procedure. Refer to Transmission Control Module Programming. Is the action complete? | Go to Step 5 | Go to Step 4 |
4 | Replace the TCM. Refer to Transmission Control Module Replacement for replacement procedures. Is the replacement complete? | Go to Step 5 | -- |
5 | Perform the following procedure to verify the repair:
Does the DTC reset? | Go to Step 6 | Go to Step 2 |
6 | Use the Tech 2 to read the DTC information. Does the Tech 2 display any DTCs that have not been diagnosed and rectified? | System OK | |
When all diagnosis and repairs are completed, clear all DTCs and verify correct operation. | |||
