Powertrain Control Module (PCM)

Powertrain Control Module (PCM):

DESCRIPTION AND OPERATION
The Powertrain Control Module (PCM) is the control center of the vehicle. It controls the following items:

^ Fuel metering system.
^ Transaxle/transmission shifting.
^ Ignition timing.
^ On-board diagnostics for powertrain functions. It constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM also performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the MIL, and store diagnostic trouble codes which identify the problem areas to aid the technician in making repairs.

The type of PCM used is a PCM 32U. The Knock Sensor Module is no longer a separate component. The PCM contains integrated knock sensor (KS) diagnostic circuitry. For more information on the integrated KS circuitry, refer to, Knock Sensor System Description.

PURPOSE
The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. Ignition Control (IC) spark timing is the PCM method of controlling spark advance and ignition dwell. To provide optimum driveability and emissions, the PCM monitors input signals from the following components in calculating Ignition Control (IC) spark timing:

^ Ignition Control module (ICM).
^ Engine Coolant Temperature (ECT) sensor.
^ Intake Air Temperature (IAT) sensor.
^ Mass Air Flow (MAF) sensor.
^ Trans Range or PNP inputs from Trans Range switch or Park/Neutral Position switch.
^ Throttle Position (TP) sensor.
^ Vehicle Speed Sensor (VSS) / Trans Output Speed Sensor (TOSS).