Automatic Transmission Diagnosis

DTC P0601

Circuit Description
A normal function of the transmission control module (TCM) is to perform an internal test that verifies the integrity of the ROM memory allocation. This diagnostic detects faults in the allocation of flash memory that contain the program and calibration by comparing a calculated checksum with a stored checksum. When the TCM detects that the calculated checksum is different from the stored checksum, DTC P0601 sets. DTC P0601 is a type A DTC.

Conditions for Running The DTC
The ignition is ON.

Conditions for Setting The DTC
The TCM EEPROM checksums do not match.

Action Taken When the DTC Sets
^ The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the first trip when the Conditions for Setting the DTC are met.
^ 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 15TC are met. The ECM stores this information as a Freeze Frame.
^ The TCM stores DTC P0601 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 P0601 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.