Engine Control Module: Description and Operation

PURPOSE
The Powertrain Control Module (PCM) monitors the signals from various input sensors and calculates the proper operating strategy for the engine operating conditions.

In addition to normal operating strategy the PCM calculates/learns an adaptive strategy that compensates for normal wearing and aging of components.

The PCM also provides for self-diagnostic testing. When the ignition is turned on the PCM is continuously checking its inputs and outputs for values out of specification. Any discrepancies are recorded as diagnostic trouble codes.

The PCM also provides for operator initiated self-tests. These tests check for specific input values and output states under defined conditions.

Note: Incorrect testing conditions and minor procedural deviations often result in false trouble codes and inaccurate information. When initiating self-tests technicians should verify that all required conditions are met.

OPERATION
The PCM continuously monitors input signals and compares these values to calibration information stored in its memory.

The PCM's calibration assembly contains the necessary programming to fine-tune the PCM's engine calibration commands to the vehicle's weight, axle ratio, and transmission application. The calibration assembly is an integral part of the PCM and is not replaceable.

The PCM determines the correct operating strategy and makes the necessary corrections to its output signals.