Powertrain Control Module (Pcm): Notes

On most vehicles, PCM is located in passenger compartment. For exact location of PCM, see PCM LOCATION in appropriate TESTS W/CODES article or COMPONENT LOCATIONS in appropriate I - SYSTEM & COMPONENT TESTING article in the ENGINE PERFORMANCE section below. The PCM contains the Arithmetic Logic Unit (ALU), Central Processing Unit (CPU), power supply and system memories.

• TESTS W/CODES - 4.3L (for Caprice Only)
• TESTS W/CODES - 5.7L (for All Models)
• SYSTEM/COMPONENT TESTS - 4.3L (Caprice Only)
• SYSTEM/COMPONENT TESTS - 5.7L (All Models)

The PCM has a "learning" ability which allows it to make minor corrections for fuel system variations. If battery power to PCM is interrupted, a vehicle performance change may be noticed. This will correct itself and normal performance will return if vehicle is allowed to "relearn" optimum control conditions. This is accomplished by driving vehicle at normal operating temperature, under part throttle, moderate acceleration and idle conditions.