Engine Controls - Self-Diagnostics: Introduction: Description
The engine used in this vehicle has controls to reduce exhaust emissions while maintaining good driveability and fuel economy. The Powertrain Control Module (PCM) is the heart of this control system. Fig 1 has a list of sensors and inputs the PCM uses to control engine components and systems.
In addition to the PCM, this vehicle contains a Body Computer Module (BCM) which is used to control various vehicle functions based on sensors and switch inputs. Information covering basic operation, diagnosis, and service of the BCM are covered in BODY COMPUTER MODULE BODY COMPUTER MODULE article.
Both the PCM and BCM have the capability to diagnose faults in the sensors, input switches, components and systems they control. When the PCM recognizes a problem, it turns ON the "Service Engine Soon" telltale lamp on the instrument panel to alert the driver that a malfunction has occurred. The PCM will also send a message to the BCM to turn ON the "Service Car" message on the Driver Information Center (DIC).