Engine Control Module: Description and Operation

PCM And PROM View:

PURPOSE
The Powertrain Control Module (PCM) is used to control fueling, idle speed, exhaust emissions, transaxle shifts, ignition timing, cooling fans and cruise control functions. The PCM has the capability to diagnose faults in the sensors, input switches, components and systems it controls. When the PCM recognizes a problem, it may turn "ON" the "SERVICE ENGINE SOON" Malfunction Indicator Lamp (MIL) on the instrument panel or send a message to the Instrument Panel Cluster (IPC) to turn "ON" the "SERVICE VEHICLE SOON" message on the Driver Information Center (DIC) to alert the deriver that a malfunction has occurred.

CONSTRUCTION
The PCM consists of two separately serviceable parts, the PCM and Programmable Read Only Memory (PROM). The PROM Plugs into the PCM and is located under the PROM cover. The PCM is connected to the engine wiring harness by three connectors. A 32-pin black connector, a 24-pin black connector and a 32-pin green connector. Each row of pins in these three connectors has been given a unique alphabetic designation, A or B (24-pin black connector), C or D (32-pin black connector) and E or F (32-pin green connector).