The heart of the electronic control system, which is found on the vehicles covered by this manual, is a computer control module. The module gathers information from various sensors, then controls fuel supply and engine emission systems. Most early model vehicles are equipped with an Engine Control Module (ECM) which, as its name implies, controls the engine and related emissions systems. Some ECMs may also control the Torque Converter Clutch (TCC) on automatic transaxle vehicles or the manual upshift light on manual transmission vehicles. Later model vehicles may be equipped with a Powertrain Control Module (PCM). This is similar to the original ECMs, but is designed to control additional systems as well. The PCM may control the manual transmission shift lamp or the shift functions of the electronically controlled automatic transmission.
Regardless of the name, all computer control modules are serviced in a similar manner. Care must be taken when handling these expensive components in order to protect them from damage. Carefully follow all instructions included with the replacement part. Avoid touching pins or connectors to prevent damage from static electricity.
Removal & Installation
- Turn the ignition switch to the OFF position.
- If the ECU is mounted under the dash, remove the left and/or right side panel from the center console, or remove the under dash panel.
- Remove the bolts holding the ECU to the mounting bracket.
- Disconnect the wiring harness from the ECU and remove ECU from the vehicle.
- Connect the electrical harness to the ECU. Make certain the multi-pin connector is firmly and squarely seated to the ECU.
- Install the ECU in the mounting bracket and secure in position.
- If necessary, install the side panels to the center console or dash panel.
- Connect the negative battery cable.