Cherokee 4WD V6-173 2.8L VIN W 2-bbl (1985)
Powertrain Control Module: Description and Operation
PROM
The ECM is the control center of the C3 system. Its function is to monitor input information from the various sensors, process this information, then
generate output commands to the various systems that affect the performance of the vehicle.
The ability of the ECM to perform these functions is dependent upon a removable calibration unit called the PROM. There are specific ECM/PROM
combinations for each vehicle and they should not be interchanged.
The ECM also performs the diagnostic function of the C3 system, alerting the driver through a ``Check Engine'' light should any problem in the system
arise and storing a code or series of codes which the technician uses as an aid in making repairs.