Electronic Control Module (ECM): Notes

NOTE: Some models use what is termed a Powertrain Control Module (PCM). The only difference between an ECM and PCM is that, in addition to electronic engine controls, the PCM also controls electronic transmission internals and cruise control system. Unless specifically stated, references to ECM also apply to PCM equipped vehicles.

On most vehicles, ECM is located in passenger compartment. For exact locations of ECM for a particular model, see ECM LOCATION in the G - TESTS W/ CODES article in this section, or refer to COMPONENT LOCATIONS in I - SYSTEM/COMPONENT LOCATIONS article in this section. The ECM consists of the Arithmetic Logic Unit (ALU), Central Processing Unit (CPU), power supply and system memories.

The ECM has a "learning" ability which allows it to make minor corrections for fuel system variations. If battery power is interrupted, a vehicle performance change may be noticed. This will correct itself and normal performance will return if vehicle is allowed to "relearn" optimum control conditions. This is accomplished by driving vehicle at normal operating temperature, under part throttle, moderate acceleration and idle conditions.