Powertrain Control Module

Powertrain Control Module (PCM):

The PCM is a digital computer containing a microprocessor. The PCM receives input signals from various switches and sensors that are referred to as PCM Inputs. Based on these inputs, the PCM adjusts various engine and vehicle operations through devices that are referred to as PCM Outputs.
PCM Inputs:
- Air Conditioning Head Pressure
- Battery Voltage
- Brake Switch
- Camshaft Position Sensor
- Crankshaft Position Sensor
- Engine Coolant Temperature Sensor
- Heated Oxygen Sensors (Upstream and Downstream)
- Intake Air Temperature Sensor (2.4L only)
- Knock Sensor (except 3.0L)
- Manifold Absolute Pressure (MAP) Sensor
- SCI Receive
- Speed Control System Controls
- Throttle Position Sensor
- Transaxle [1][2]Park/Neutral Position Switch (automatic transaxle)
- Transmission Control Module
- Vehicle Speed Sensor

PCM Outputs:
- Air Conditioning Clutch Relay
- Automatic Shutdown (ASD) Relay
- Data Link Connector
- Proportional Purge Solenoid
- Electric EGR Transducer
- Fuel Injectors
- Fuel Pump Relay
- Generator Field
- Idle Air Control Motor
- Ignition Coil
- Leak Detection Pump
- Malfunction Indicator (Check Engine) Lamp
- Radiator Fan Control Module
- Speed Control Solenoids
- Tachometer Output
- Torque Converter Clutch Solenoid (3 speed transmission)
- Transmission Control Module

Based on inputs it receives, the PCM adjusts fuel injector pulse width, idle speed, ignition spark advance, ignition coil dwell and canister purge operation. The PCM regulates the cooling fan, air conditioning and speed control systems. The PCM changes generator charge rate by adjusting the generator field.

The PCM adjusts injector pulse width (air/fuel ratio) based on the following inputs:
- Battery voltage
- Engine coolant temperature
- Exhaust gas content (oxygen sensors)
- Engine speed (crankshaft position sensor)
- Manifold absolute pressure
- Throttle position

The PCM adjusts ignition timing based on the following inputs.
- Barometric pressure
- Engine coolant temperature
- Engine speed (crankshaft position sensor)
- Intake air temperature (2.4L only)
- Manifold absolute pressure
- Throttle position
- Transaxle gear selection (park/neutral switch)

The PCM also adjusts engine idle speed through the idle air control motor based on the following inputs.
- Air conditioning select switch head pressure
- Brake switch
- Engine coolant temperature
- Engine speed (crankshaft position sensor)
- Manifold absolute pressure
- Throttle position
- Transaxle gear selection (park/neutral switch)
- Vehicle distance (speed)

The Automatic Shutdown (ASD) and fuel pump relays are located in the Power Distribution Center (PDC).

The camshaft position sensor (distributor pick-up signal 3.0L) and crankshaft position sensor signals are sent to the PCM. If the PCM does not receive both signals within approximately one second of engine cranking, it deactivates the ASD relay and fuel pump relay. When these relays are deactivated, power is shut off to the fuel injectors, ignition coil, oxygen sensor heating element and fuel pump.

The PCM contains a voltage converter that changes battery voltage to a regulated 8.0 volts to power the camshaft position sensor, crankshaft position sensor and vehicle speed sensor. The PCM also provides a 5.0 volt supply for the manifold absolute pressure sensor, throttle position sensor and engine coolant temperature sensor.