Circuit Description
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
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.