Powertrain Control Module (PCM) Programming

EEPROM Data Storage Unit
The PCM contains a data storage unit which can save critical data even when battery power is removed. This unit, the Electrically Erasable Programmable Read Only Memory (EEPROM) is used by the PCM to store Throttle Position (TP) Sensor learned value, Transaxle Shift Adapt values, and Transaxle Oil Life Index.

These values are stored in the EEPROM during the first 30 seconds after the key is turned OFF. Therefore, you should wait at least 30 seconds after key OFF before disconnecting the battery to allow these values to be stored in the EEPROM.

Important: Disconnecting the battery before the PCM is able to store the values may result in EEPROM reset, DTC P1526 and transaxle oil life and engine oil life being reset to 0.

PCM and Flashing The EPROM

Important: The service PCM will not contain data. The EPROM must be flashed after the service PCM is installed.

Powertrain Diagnsois
This powertrain has very complex components with equally complex operating characteristics. Therefore, it is essential that the Powertrain diagnostic procedures be used for diagnosis before any repairs are made. While the PCM may appear on the surface to be the source of a problem, it may, in fact, be operating properly based on incorrect inputs it receives. Powertrain diagnostic procedures are designed to arrive at the CORRECT repair as QUICKLY as possible. DO NOT, under any circumstances, replace a PCM unless directed to do so by diagnostic procedures or other service information sources.

PCM Service Options
Service of the PCM will consist of either replacement of the PCM and flashing the EPROM. If a diagnostic procedure calls for the PCM to be replaced, the PCM should be checked first to see if it is the correct part. The EPROM can also be flashed when called for. When flashing the EPROM, also refer to the latest technical service bulletins for updated programming procedures and information.

Notice: To prevent internal PCM damage, the ignition must be in the OFF (LOCK) position when disconnecting or reconnecting power to the PCM, as when the battery cables, PCM connectors, or fuses are connected or disconnected.

EEPROM Service
The EPROM and the EEPROM are soldered into the PCM and cannot be serviced separately.

EEPROM Data Following PCM Replacement

EEPROM Reset
Since the data contained in the EEPROM is specific to the vehicle that the PCM is in, the EEPROM should reset if the PCM is installed in another vehicle. When this reset occurs, the following data will be erased:

^ TP sensor learn
^ Transaxle adapts (shifts, steady state, and garage shifts)
^ Transaxle oil life
^ Engine oil life
^ PCM odometer reading

Reset Messages
Resetting TP sensor learn will trigger DTC P1526. Resetting transaxle oil life will trigger the Change Trans Fluid message. Resetting engine oil life will trigger the Change Engine Oil Now message. The TP sensor learn can be relearned by following the DTC P1526 table. The transaxle oil life may be reset to its previous value using PCM transaxle oil life override. The engine oil life may be reset to 100 by displaying the Oil life left and pressing the Reset button. The transaxle adapts will be relearned during normal operation. The odometer must be reset with a scan tool.

After Repair Inspection
After replacement of a PCM and/or flashing the EPROM, clear PCM DTCs and check the vehicle for proper operation. Poor engine performance, surging, loss of cruise control, improper SERVICE ENGINE SOON MIL operation, no starts, and/or hard starts may be caused by an improperly flashed EPROM, in which case DTC P0602 may set and the vehicle may not start.