Engine Control Module: Testing and Inspection

PCM EPROM
The PCM contains an EPROM (Electrically Programmable Read Only Memory) that contains the calibration information used by the PCM to control fueling, idle speed, ignition timing, transaxle shifts and emissions. This calibration information is based on various aspects of the vehicle such as engine size, vehicle weight, transaxle type, final drive ratio, etc. The EPROM is programmed (Flashed) with this critical information.

Replacement PCM
Replacement PCMs 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 technical service bulletins be referenced for information concerning any new procedures or EPROM programs.

PCM Fails to Program
If the current program or an attempted reprogramming fails on the PCM, it will set DTC P0602, which is diagnosed in System Diagnosis / Procedures / Diagnostic Tables. Refer to the Service and Repair for information pertaining to PCM service procedures. Testing and Inspection