Symptom Related Diagnostic Procedures

Diagnostic Chart:

Wiring Diagram:

Circuit Description
When the ignition switch is first turned to OFF/UNLOCK or RUN, IGNITION 1 voltage is applied from the CLS/PCM fuse to the INDICATORS bus in the Instrument Panel Cluster (IPC). The ground side of the AIR BAG indicator (LED) is controlled by the instrument cluster microprocessor. When the ignition switch is in the OFF/UNLOCK position, the serial data line (CKT 800) is not operative. This condition will cause the IPC microprocessor to turn the AIR BAG (as well as the SEAT BELT) indicator ON steady. When the ignition switch is first turned to RUN, the AIR BAG Fuse applies battery voltage to the IGNITION 1 input, terminal 10. The inflatable restraint sensing and diagnostic module (SDM) responds by flashing the AIR BAG indicator (via the serial data line) seven times. If IGNITION 1 is outside of the normal operating voltage range (8.2.-17.1 volts), the AIR BAG indicator will come ON steady with no DTCs set.

Diagnostic Aids
If the serial data line is malfunctioning, the AIR BAG indicator will come on steady. If the inflatable restraint sensing and diagnostic module (SDM) connector is not properly connected to the SDM, the AIR BAG indicator will come ON steady.

When measurements are requested in this table, use J 39200 Digital Multimeter with the correct terminal adapter from J 35616-A Connector Test Adapter Kit. When a check for proper connection is requested, refer to Intermittents and Poor Connections. When a wire, connector or terminal repair is requested, use J 38125-A Terminal Repair Kit and refer to Wiring Repair. Intermittent Problems Service and Repair

Test Description
The numbers below refer to the step numbers on the diagnostic table:
3. This test checks for a malfunction in the serial data line (CKT 800).
4. This test checks for sufficient IGNITION 1 voltage applied to the SDM.
5. This test checks for excessive IGNITION 1 voltage applied to the SDM.
6. This test checks for a proper connection at the SDM.
8. An open AIR BAG Fuse would cause the AIR BAG warning lamp to come on steady.
9. This test checks whether a short to ground caused the AIR BAG Fuse to open.
10. This test determines whether the short to ground is due to a short in the wiring or internal to the SDM.
14. This test checks for an open in the IGNITION 1 circuit, CKT 1139.