Trouble Codes

In the process of controlling the various subsystems, the ECM and the BCM continually monitor operating conditions for possible system malfunctions. By comparing system conditions against standard operating limits, certain circuit and component malfunctions can be detected.

A 3-digit numerical "Trouble Code" is stored in computer memory when a problem is detected. These trouble codes can later be displayed to aid the technician in diagnosing the system. This display of diagnostic trouble codes can only be accessed in the "Service Mode".

Certain system malfunctions cause computer controlled diagnostic messages and/or telltales to appear indicating that service is required. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and the BCM provides certain back-up functions known as "Failsoft". A typical "Failsoft" action would be the substitution of a fixed input value when a sensor is detected to be open or short.