Transmission Diagnosis

DTC P0604
Circuit Description
A normal function of the Transmission Control Module (TCM) is to perform an internal test that verifies the read and write capability of the Random Access Memory (RAM). This diagnostic detects faults in the RAM by writing test data to the RAM, reading back the same data, and then comparing the two data sets. When the TCM detects that the data that was read from the RAM is different from the test data that was written to the RAM, DTC P0604 sets. DTC P0604 is a type A DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0604 Transmission Control Module (TCM) Random Access Memory (RAM)

Conditions for Running The DTC
The ignition is ON.

Conditions for Setting The DTC
The data read from RAM does not match the test data written to the RAM.

Action Taken When the DTC Sets
^ The TCM requests the ECM to illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive drive trip in which 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 TCC commands maximum line pressure.
^ The TCC freezes transmission adaptive functions.
^ 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 P0604 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 P0604 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.