General System Description

DESCRIPTION
The Powertrain Control Module (PCM) controls spark advance and fuel injection for all driving conditions. The PCM monitors input signals from the following components as part of its ignition control function to determine the required ignition timing:

^ Ignition Control Module (IC Module).
^ Engine Coolant Temperature (ECT) sensor.
^ Manifold Absolute Pressure (MAP) sensor.
^ Transaxle Range (TR) switch.
^ Throttle Position (TP) sensor.
^ Vehicle Speed Sensor (VSS).
^ Knock Sensor (KS).


Outputs
Their are two types of PCM outputs, device outputs and output signals. Device outputs are components that the PCM controls their function as either ON / OFF or with a Pulse Width Modulated signal that can vary the components operation. Output signals are used by the PCM to communicate certain operating conditions with other modules in the vehicle. Output signals can also be ON I OFF or PWM type signals.

The PCM typically controls both the device outputs and the output signals by completing the ground path of the circuit. Most outputs are monitored for failures and will set a DTC. A scan tool can also command most of the outputs ON in order to diagnose failures.

PCM device outputs include the following:

^ The Fuel Pump relay.
^ The Fuel Injectors.
^ The EGR Valve.
^ The EVAP Purge Solenoid.
^ The EVAP Vent Valve.
^ The Idle Air Control valve.
^ The A/C Compressor Clutch relay.
^ The Cooling Fan relays.
^ The MIL lamp.
^ The transmission solenoids.

PCM output signals include the following:
^ Vehicle Speed output.
^ Cruise Inhibit output.
^ Fuel Enable output.
^ Starter Inhibit output.
^ Delivered Torque output.