Self-Diagnostic System: Notes

Self-diagnostic system consists of 4 sub-systems. These sub-systems are Powertrain Control Module (PCM), Instrument Panel Cluster (IPC) options, A/C Programmer (ACP) options and Supplemental Inflatable Restraint (SIR) system.

In addition to monitoring a particular set of sensors and switches, PCM maintains continuous communication with each sub-system component. Should a component exceed pre-programmed limits, PCM will recognize a malfunction and may act to control malfunctioning component. To control a particular sub-system, PCM rapidly switches an internal circuit between zero and 5 volts, converting programmed control information into series of pulses that represents coded serial data messages. These messages are transmitted to malfunctioning sub-system, which interprets information and responds accordingly.

As a result, an alphanumeric code, known as a trouble code, is often set in PCM memory. This trouble code identifies malfunctioning component and can be accessed by a service technician as an aid to diagnostic procedures. All trouble codes are displayed on Driver Information Center (DIC) panel.

In addition to monitoring self-diagnostic system and displaying trouble codes, PCM can be programmed by service technician to perform specific diagnostic tests on individual components and sub-systems. Results of these tests are displayed on DIC. This article covers accessing PCM trouble codes and programming self-diagnostic system to perform specific diagnostic tests on system components.