Engine Control Module: Description and Operation

Fig. 2 ECM Terminal Identification:

PURPOSE
The ECM processes information from sensors and switches and adjusts vehicle performance systems accordingly.

Programmable Read Only Memory (PROM)
The PROM contains the program used by the ECM to generate output commands depending on varying operating conditions.
- ECM function is dependent upon the PROM installed.
- ECM/PROM combinations are vehicle specific and should not be interchanged.

Diagnostic Function
- The ECM illuminates the "Check Engine" light to alert the driver of problems detected in any monitored circuit.
- The ECM also stores a diagnostic trouble code or a series of codes corresponding to the problem detected.