For a complete wiring diagram Refer to Section 8W.After the controller is reset (ignition turned to the RUN position) the microprocessor checks the integrity of the program memory (ROM). A checksum is calculated by adding all used bytes in the program memory. The sum should be the same as a known constant stored in the program memory.When Monitored:One time after the controller is reset (ignition turned to the RUN position).Set Condition:Whenever the Powertrain Control Module (PCM) detects an internal controller problem.Possible CausesPOWER OR GROUND CIRCUITPOWERTRAIN CONTROL MODULEAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE) 1. CHECK WIRING AND CONNECTORS FOR INTERMITTENT OPERATIONUsing the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits.Wiggle the wires while checking for shorted and open circuits.Check for any Service Bulletins that may apply.Were there any problems found?YesRepair the power and/or ground circuits as necessary.Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE) NoReplace the PCM per the Service Information. With the scan tool, perform QUICK LEARN.Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)