SIR Diagnostic Trouble Code Logic

CAUTION: In order to avoid deploying the air bag when troubleshooting the SIR system, use only the equipment specified and the instructions given. Failure to use the specified equipment as instructed could cause air bag deployment, personal injury to you or someone else, or unnecessary SIR system repairs.

DIAGNOSTIC TROUBLE CODES (DTC)
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 Electrically Erasable Programmable Readable Memory(EEPROM).
Any DTC beginning with a U is a Serial Data Line Class 2 State Of Health (SOH) DTC. The State of Health (SOH) DTCs indicate a Serial Data Line Class 2 malfunction. The State of Health (SOH) DTCs will not cause the AIR BAG warning lamp to come ON. Normally they will accompany a SIR DTC. Once the malfunction which caused the SIR DTC to set is repaired, the SOH DTC may clear.