The Powertrain Control Module (PCM) is located in the engine compartment attached to the dash panel.
The Powertrain Control Module (PCM) operates the fuel system. The PCM is a pre-programmed, triple microprocessor digital computer. It regulates ignition timing, air-fuel ratio, emission control devices, charging system, certain transmission features, speed control, air conditioning compressor clutch engagement and idle speed. The PCM can adapt its programming to meet changing operating conditions
The PCM receives input signals from various switches and sensors. Based on these inputs, the PCM regulates various engine and vehicle operations through different system components. These components are referred to as Powertrain Control Module (PCM) Outputs. The sensors and switches that provide inputs to the PCM are considered Powertrain Control Module (PCM) Inputs.
The PCM adjusts ignition timing based upon inputs it receives from sensors that react to: engine rpm, manifold absolute pressure, engine coolant temperature, throttle position, transmission gear selection (automatic transmission), vehicle speed, power steering pump pressure, and the brake switch.
The PCM adjusts idle speed based on inputs it receives from sensors that react to: throttle position, vehicle speed, transmission gear selection, engine coolant temperature and from inputs it receives from the air conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts ignition coil dwell. The PCM also adjusts the generator charge rate through control of the generator field and provides speed control operation.
Removal & Installation
- Before servicing the vehicle, refer to the Precautions Section.
- Disconnect negative battery cable at battery.
- Remove cover over electrical connectors. Cover snaps onto PCM.
- Carefully unplug the three 32 way connectors (four 38-way connectors if equipped with NGC) from PCM.
Remove three PCM mounting bolts and remove PCM from vehicle.
- Install PCM and 3 mounting bolts to vehicle.
- Tighten bolts. Refer to torque specifications.
- Check pin connectors in the PCM and the three 32-way connectors (four 38-way connectors if equipped with NGC) for corrosion or damage. Also, the pin heights in connectors should all be same. Repair as necessary before installing connectors.
- Install three 32-way connectors (four 38-way connectors if equipped with NGC).
- Install cover over electrical connectors. Cover snaps onto PCM.
- Install negative battery cable.
The 5.7L V-8 engine is equipped with a fully electronic accelerator pedal position sensor. If equipped with a 5.7L, also perform the following 3 steps:
- Connect negative battery cable to battery.
- Turn ignition switch ON, but do not crank engine.
- Leave ignition switch ON for a minimum of 10 seconds. This will allow PCM to learn electrical parameters.
- The scan tool may also be used to learn electrical parameters. Go to the Miscellaneous menu, and then select ETC Learn.
- If the previous step is not performed, a Diagnostic Trouble Code (DTC) will be set.
- If necessary, use a scan tool to erase any Diagnostic Trouble Codes (DTC's) from PCM. Also use the scan tool to reprogram new PCM with vehicles original Vehicle Identification Number (VIN) and original vehicle mileage.
Service of the Powertrain Control Module (PCM) should consist of either replacement of the PCM or programming. If the diagnostic procedures call for the PCM to be replaced, the replacement PCM should be checked to ensure that the correct part is being used. If the correct part is being used, remove the faulty PCM and install the new service PCM.
Check for possible causes before replacement of PCM as follows:
(A918) Fused B (+) circuit open or shorted