Transmission Diagnosis

Circuit Description with 4L30-E Automatic Transmission
A normal function of the Transmission Control Module (TCM) programming is to perform an internal check that verifies the integrity of the EEPROM memory and data allocations. When the TCM detects the calculated checksum is different from the EEPROM checksum after reprogramming the TCM or after power-up sequence, then DTC P0602 will set. DTC P0602 is a type B DTC.

CONDITIONS FOR RUNNING THE DTC

Condition 1:
The ignition switch is in the RUN position.

Condition 2:
The ignition switch is in the OFF position.

CONDITIONS FOR SETTING THE DTC

Condition 1:
TCM EEPROM checksum is incorrect.

Condition 2:
TCM is unable to write to the EEPROM.

ACTION TAKEN WHEN THE DTC SETS
^ The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.
^ The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.
^ The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

CONDITIONS FOR CLEARING THE MIL/DTC
^ The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.
^ A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.
^ The scan tool clears the MIL/DTC.
^ The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

DIAGNOSTIC AIDS
If TCM reprogramming was just completed, then this could be the reason for this code setting.

TEST DESCRIPTION

Diagnostic Chart:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that an operational abnormality, such as Electromagnetic Interference (EMI), did not take place during TCM power up.
3. This step reprograms the TCM. If after reprogramming the DTC resets, then the TCM must be replaced.