How to Display and Read Diagnostic Trouble Codes
The diagnostic procedures used in this section are designed to find and repair air bag system malfunctions. To get the best results, it is important to use the diagnostic charts and follow the sequence listed below.
A. PERFORM THE "AIR BAG DIAGNOSTIC SYSTEM CHECK."
The "Air Bag Diagnostic System Check" must be the starting point of any air bag system diagnostics. The "Air Bag Diagnostic System Check" checks for proper "AIR BAG" warning lamp operation, the ability of the SDM to communicate through the "Serial Data" line and whether air bag diagnostic trouble codes exist.
B. REFER TO THE PROPER DIAGNOSTIC CHART AS DIRECTED BY THE "AIR BAG DIAGNOSTIC SYSTEM CHECK."
The "Air Bag Diagnostic System Check" will lead you to the correct chart to diagnose any air bag system malfunctions. By passing these procedures may result in extended diagnostic time, incorrect diagnosis and incorrect parts replacement.
C. REPEAT THE "AIR BAG DIAGNOSTIC SYSTEM CHECK" AFTER ANY REPAIR OR DIAGNOSTIC PROCEDURES HAVE BEEN PERFORMED.
Performing the "Air Bag Diagnostic System Check" after all repair or diagnostic procedures will ensure that the repair has been made correctly and that no other malfunctions exist.
CIRCUIT DESCRIPTION:
- When the ignition switch is first turned "ON", "Ignition 1" voltage is applied from the "AIR BAG-IG" fuse to the SDM at the "Ignition 1" input terminal "B9" and from the "IG" fuse to the SDM at the "Redundant Indicator Ignition 1" input terminal "A4". The SDM responds by flashing the "AIR BAG" warning lamp seven times while performing tests on the air bag system.
- When the engine is being cranked, "Ignition 1" voltage is applied from "AIR BAG-ST" fuse to the SDM at the "Crank" input terminal "B1". The SDM responds by grounding the "AIR BAG Indicator (AIR BAG warning lamp)" output terminal "A9" until "Ignition 1" voltage is removed from the "Crank" input. This results in the "AIR BAG" warning lamp being "ON" steady during cranking. After cranking the SDM will flash the "AIR BAG" warning lamp six times and perform tests on the air bag system.
NOTES ON SYSTEM CHECK CHART:
1. The "AIR BAG" warning lamp should flash seven times after ignition is first turned "ON."
2. The "AIR BAG" warning lamp should remain "ON" steady during cranking.
3. After cranking, the "AIR BAG" warning lamp should flash six times then go "OFF."
4. This test checks for the proper operation of the "Serial Data" line. This test will also determine whether history diagnostic trouble codes are stored and, if so, identify them.
5. When the "AIR BAG" warning lamp flashes four times during "Bulb Check" this indicates a malfunction in the redundant lamp driver circuitry. These malfunctions are diagnosed by DTC 62 chart.
6. Improper Operation of the "AIR BAG" warning lamp is indicated. This test differentiates a warning lamp stays "ON" condition from a warning lamp does not come "ON" condition.
7. This test checks for proper operation of the "Serial Data" line. This test will also identify the stored diagnostic trouble codes and whether they are current or history.
DIAGNOSTIC AIDS:
- The order in which diagnostic trouble codes are diagnosed is very important. Failure to diagnose the diagnostic trouble codes in the order specified may result in extended diagnostic time, incorrect diagnosis and incorrect parts replacement.