EPROM

The PCM houses an EPROM (Erasable Programmable Read Only Memory) that contains the calibration information used by the PCM to control the following processes:

^ Fueling
^ Idle speed
^ Ignition timing
^ Transaxle shifts
^ Emissions

This calibration information is based on various aspects of the vehicle. The list below includes some of the aspects that affect the calibration information:

^ Engine size
^ Vehicle weight
^ Transaxle type
^ Final drive ratio

The EPROM is programmed (Flashed) with this critical information. Replacement PCM's used for service come without the programming, which must be performed by the technician using the latest diagnostic tools and programs. Additionally, in certain situations, the diagnosis may require the technician to reprogram (Flash) the PCM in an attempt to eliminate a DTC or condition. Therefore, it is crucial that the latest service publications (bulletins, service manuals, etc.) be referenced for information concerning any new procedures or EPROM programs.

If the current program or an attempted reprogramming fails on the PCM, it will set DTC P0602. Refer to the DTC P1627 Control Module Long Term Memory Performance.