Electronic Control System
WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
The 6.6L diesel models use an Electronic Control Module (ECM), and 8.1L gasoline models use a Powertrain Control Module (PCM). For the purpose of this article, PCM will be used throughout to indicate all engine control modules. A separate Transmission Control Module (TCM) is also used on models using the Allison transmission.
The PCM constantly monitors the information from various sensors, and controls the systems that affect vehicle performance and emissions. The PCM also performs the diagnostic functions for those systems. The PCM can recognize operational problems and alert the driver through the Malfunction Indicator Lamp (MIL) when a malfunction has occurred. When a malfunction is detected, the PCM stores a Diagnostic Trouble Code (DTC) which helps to identify problem areas. This is done to aid the technician in making repairs.