Symptom Related Diagnostic Procedures

AIR BAG Warning Lamp Circuit Malfunction (Part 1 Of 2):

AIR BAG Warning Lamp Circuit Malfunction (Part 2 Of 2):

Wiring Diagram:

CIRCUIT DESCRIPTION
The ignition switch supplies ignition 1 voltage to the inflatable restraint Sensing and Diagnostic Module (SDM) at terminal A1 using the AIR BAG Fuse. The ignition switch also supplies ignition 1 voltage to the instrument cluster. The AIR BAG warning lamp is controlled by the SDM via Class 2 serial data. When the ignition switch is first turned ON, the instrument cluster flashes the AIR BAG warning lamp seven times. Next, the SDM performs tests on the SIR system then commands the instrument cluster to turn OFF the AIR BAG warning lamp after it has flashed seven times. If the ignition 1 voltage is outside of the normal operating voltage range (9-16 V), the SDM will command the instrument cluster to turn ON the AIR BAG warning lamp with no DTCs present.

DIAGNOSTIC AIDS
The loss of serial data communication between the SDM and the instrument cluster will cause the AIR BAG warning lamp to come ON solid. Refer to A Diagnostic System Check - Data Link Communications in Data Link Communications.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
3. This step checks to see if the AIR BAG warning lamp flashes seven times when the ignition is turned ON.
5. This step checks to see if DTC U1088 is present in the instrument cluster.
6. This step checks to see if the AIR BAG warning lamp is being commanded ON.
7. This step checks to see if the ignition voltage to the SDM is more than 9 V.
8. This step determines if the ignition voltage to the SDM is more than 16 V or if there is a malfunctioning SDM.
9. This step checks to see if the SDM wiring harness connector exhibits signs of corrosion, terminal damage, or poor connections.
11. This step checks to see if there is an open or a high resistance in the B+ feed circuit to the SDM.
13. This step checks to see if there is an open or a high resistance in the B+ feed circuit to the AIR BAG Fuse.
15. This step determines if there is an open or a high resistance in the SDM ground circuit or if there is a malfunctioning SDM.