2001 Cadillac STS speedometer jumps and shifts hard

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) copies the program information stored in the Electrically Erasable Programmable Read Only Memory (EEPROM) to the random access memory (RAM). This allows the PCM to work with, and make any updates to the information. The PCM tests all areas of the RAM. If the PCM detects an error in any area of the RAM, this Diagnostic Trouble Code (DTC) will set.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The PCM detects a malfunction in the RAM area.

ACTION TAKEN WHEN THE DTC SETS
The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL and the DTC.
DIAGNOSTIC AIDS
DTC P0604 indicates that the RAM or an area of the RAM has malfunctioned. The PCM must be replaced. Remember to program the replacement PCM with the correct software and calibration for the vehicle.

I would start here as the pcm has failed

Roy

A shop as it will have to be programmed by them anyway

Roy