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
2.7L, 3.5L & 5.7L Engines
- Disconnect the negative battery cable.
- Remove the PCM bracket-to-body mounting bolt.
- Lift up the PCM assembly.
- Unlock and disconnect the electrical connectors from PCM.
- Remove the assembly from vehicle.
- Remove bracket from PCM.
- Remove the rubber bumper from PCM.
- Install rubber bumper to PCM back.
- Check pins in electrical connectors for damage.
- Repair pins as necessary.
- Install the electrical connectors to PCM.
- Install the mounting bracket to PCM.
- Install the assembly to body.
- Tighten mounting bolt to 80 inch lbs. (9 Nm).
- Connect negative cable to battery.
2.7L, 3.5L & 5.7L Engines
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:
(A209) Fused B (+) circuit open or shorted