Tahoe 4WD V8-393 6.5L DSL Turbo VIN S (1995)
Engine Control Module: Service and Repair
Powertrain Control Module (PCM) Replacement
Powertrain Control Module
PCM And Prom
Service of the Powertrain Control Module (PCM) should normally consist of either replacement of the PCM or a Programmable Read Only
Memory (PROM) change. If the diagnostic procedures call for the PCM to he replaced, the PROM and PCM should be checked first to see if they
are the correct parts. If they are, remove the PROM from the faulty PCM and install it in the new service PCM. THE SERVICE PCM WILL NOT
CONTAIN A PROM. Diagnostic Trouble Code (DTC) 51 indicates the PROM is installed improperly or has malfunctioned. When DTC 51 is
obtained, check the PCM installation for bent pins or pin not fully seated in the socket. If it is installed correctly and DTC 51 is still displayed,
replace the PROM.
CAUTION:
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To prevent possible electrostatic discharge to the PCM or PROM, do not touch the component leads, and do not remove integrated circuit from
carrier.
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When replacing the production PCM with a service PCM (controller), it is important to transfer the broadcast code and production PCM
number to the service PCM label. Please Do Not record on PCM cover. This will allow positive identification of PCM parts throughout the
service life of the vehicle.
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To prevent internal PCM damage, the ignition must be "OFF" when disconnecting or reconnecting power to PCM (for example, battery cable,
PCM pigtail, PCM fuse, jumper cables, etc.). The ignition should be "OFF" for at least 30 seconds before disconnecting power to the PCM.
NOTE: When replacing the production PCM with a service PCM, a DTC 88 will be stored. It is important to program TDC Offset into the
service PCM. Refer to TDC Offset Program Procedure. See: TDC Offset Program Procedure
