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 diagnostics 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. DTC P0602 is a type A DTC.
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 ECM to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM turns off power to all 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 TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
| • | Powertrain braking is disabled. |
| • | The TCC is disabled. |
| • | 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 P0602 in TCM history. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after the sixth 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 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.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Automatic Transmission? | -- | Go to Step 2 | |||||
2 |
Important:
Did DTC P0602 reset? | -- | Go to Step 3 | Go to Diagnostic Aids | ||||
Perform the Transmission Control Module Reprogramming Procedure. Refer to Service Programming System (SPS) in Programming. Is the action complete? | -- | Go to Step 5 | Go to Step 4 | |||||
4 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 5 | -- | ||||
5 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 6 | Go to Step 2 | ||||
6 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
