Self-Diagnostic System Description

NOTE: Assembly Line Data Link (ALDL) connector is now referred to as Data Link Connector (DLC).

The self-diagnostic system consists of several components. These components include the Powertrain Control Module (PCM), Instrument Panel Cluster (IPC), A/C Programmer (ACP), supplemental inflatable restraint system's Diagnostic Energy Reserve Module (DERM) and Road Sensitive Suspension (RSS) module (4.6L) or Speed Sensitive Suspension (SSS) module (4.9L). Also included in the self-diagnostic system on vehicles equipped with Anti-Lock Brake System (ABS) is the Electronic Brake Control Module (EBCM - 4.9L) or Electronic Brake & Traction Control Module (EBTCM - 4.6L).

In addition to monitoring a particular set of sensors and switches, the IPC maintains continuous communication with each of the other main components of the computer system. The other main components monitor other related sets of sensors and switches, reporting all system conditions to each of the main components continually through serial data line.

Should any IPC subsystem component exceed pre-programmed limits, the IPC will recognize the malfunction and may either exert some control over the component or, in the case of sensors, replace the sensor information with a standard or default value, which will allow the system to continue to function until servicing is possible. As a result of these interactions between the IPC and a malfunctioning component, an alpha-numeric code, known as a trouble code, is often set in the IPC's memory. Trouble code identifies the malfunctioning component and code can be accessed by a service technician as an aid to diagnostic procedures. All trouble codes are displayed on the Climate Control Center (CCC).

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