Accessing and Reading Diagnostic Trouble Codes

DIAGNOSTIC TROUBLE CODES

The "SIR Diagnostic System Check" must always be the starting point of any SIR system diagnosis. The "SIR Diagnostic System Check" checks for proper "AIR BAG" warning lamp operation and checks for SIR diagnostic trouble codes using the scan tool.

1. Current diagnostic trouble codes - Malfunctions that are presently being detected. Current diagnostic trouble codes are stored in RAM (Random Access Memory).

2. History diagnostic trouble codes - All malfunctions detected since the last time the history memory was cleared. History diagnostic trouble codes are stored in EEPROM.

On-Board Diagnostics

If you are unfamiliar with the ON-BOARD DIAGNOSTIC SYSTEM, refer to BODY CONTROL MODULE where complete information regarding its operation is included before attempting to read SIR Diagnostic Trouble Codes(DTCs). Briefly, DTC display works as follows. Body Control Module

To display DTCs, the ignition switch must be "ON." Depress the "OFF" and "WARMER"(digital cluster), "PASSENGER WARMER" (analog cluster) buttons of the Climate Control Center simultaneously until all the segments of the display are "ON." The Instrument Panel Cluster (IPC) will display the DTCs in the following manner:

1. All DTCs which are set. Each DTC will be displayed with its status, current or history.

2. The order of system DTC display will be PCM, IPC, Air Control Module (ACM), SDM, Traction Control System (TCS), Road Sensing Suspension (RSS), Body Control Module (PZM), Integrated Radio Control Module (IRC), RFA, CCP, Cellular Telephone (PHN).

3. Depressing the "LO" button will display the next available system selection.

Scan Tool Diagnostics

A scan tool is used to read current and history diagnostic trouble codes and to clear all diagnostic trouble codes after a repair is completed. The scan tool must be updated to communicate with the SIR system through a replaceable cartridge before it can be used for SIR diagnostics. A Vehicle Interface Module (VIM) is required to communicate with this vehicle using a Tech 1. To use the scan tool, connect it to the data link connector and turn the ignition switch "ON." The scan tool reads serial data from the SDM "Serial Data" output terminals "A3" and "B3" to the data link connector terminal "9" over the UART line.