SIR Diagnostic Trouble Code Logic

The SIR Diagnostic System Check must always be the starting point of any SIR and side air bag system diagnosis. The SIR Diagnostic System Check checks for proper AIR BAG warning lamp operation and checks for SIR and side air bag 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 Read Only 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.