General System Description

GENERAL DESCRIPTION
The Powertrain Control Module (PCM) is located on the right hand side fender well. The PCM is the control center for the fuel emissions and automatic transmission control functions. The PCM constantly monitors the information from the various sensors.

The PCM controls the component systems which affect the engine and transmission operations. The PCM alerts the driver through the Malfunction Indicator Lamp (MIL). The PCM stores the Diagnostic Trouble Codes (DTCs) which identify the problem areas. Refer to Powertrain Control Module and Powertrain Control Module for further information on using the diagnostic function of the PCM.

^ Refer to Transmission for the diagnosis of the automatic transmission.
^ Refer to Anti-lock brakes for diagnosis of the brake system.

The PCM in this vehicle is programmable. The only services allowed on the PCM is a control module replacement with a Knock Sensor (KS) calibrator PROM transferred or a KS calibrator PROM only. The KS calibrator PROM contains the up integrated knock sensor calibration.

The Electronically Erasable Programmable Read Only Memory (EEPROM) in the PCM stores the 4 calibrations. When replacing the PCM, program the EEPROM. Transfer the KS calibrator PROM to the new PCM. Refer to PCM Replacement/Programming. Service and Repair

MALFUNCTION INDICATOR LAMP (MIL)
The MIL (Malfunction Indicator Lamp) is on the instrument panel. The MIL has the following functions:

^ The MIL informs the driver that a fault that affects the vehicle's emission levels has occurred. The owner should take the vehicle for service as soon as possible.
^ As a bulb and system check, the MIL (Malfunction Indicator Lamp) comes on with the key on and the engine not running. When the engine is started, the MIL turns off if no DTCs are set.

When the MIL remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, perform an On-Board Diagnostic (OBD) System Check. The procedures for these checks are given in engine controls. These checks expose faults which the technician may not detect if other diagnostics are performed first.

DIAGNOSTIC INFORMATION
The diagnostic Tables and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The Tables are prepared with the assumption that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present.

There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in this manual. The language of communicating the source of the malfunction is a system of diagnostic trouble codes. When a malfunction is detected by the control module, a diagnostic trouble code will set and the Malfunction Indicator Lamp (MIL) Malfunction Indicator Lamp will illuminate on some applications.

CONTROL MODULE LEARNING ABILITY
The control module has a "learning" ability which allows the control module to make corrections for minor variations in the fuel system in order to improve driveability. Whenever the battery cable is disconnected, the "learning" process resets. The driver may note a change in the vehicle's performance. In order to allow the PCM to "re-learn" to drive the vehicle at part throttle with moderate acceleration. The vehicle may also operate at idle conditions until the normal performance returns.