Reading and Clearing 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 (Electrically Erasable Programmable Read-Only Memory).


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 may need to be updated to communicate with the SIR system through a replaceable cartridge before it can be used for SIR diagnostics. 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 DERM "Serial Data" output terminal "A11" at the data link connector.

A scan tool can also provide SIR system circuit values using the "Data List" function. These values are referred to in the diagnostic trouble code tables to aid in diagnosing certain SIR system malfunctions. For additional information, refer to the scan tool instruction manual.