Symptom Related Diagnostic Procedures

Diagnostic Chart:

Wiring Diagram:

Circuit Description
When the ignition switch is first turned to RUN, the SDM Fuse applies battery voltage to the inflatable restraint Sensing and Diagnostic Module (SDM) at the Ignition Positive Voltage input, terminal 3. Battery voltage is also applied to the Instrument Panel Cluster (IPC). The IPC responds by flashing the AIR BAG warning lamp seven times. The SDM performs tests on the SIR system while the IPC is flashing the warning lamp. If the SDM detects no malfunctions, the SDM commands the IPC to turn the warning lamp OFF. If the SDM detects a malfunction, the SDM commands the IPC to turn the warning lamp ON. The SDM commands the IPC over the Serial Data Line Class 2.

Diagnostic Aids
If the IPC receives no message from the SDM the IPC will do the following when the ignition is turned to RUN:

^ Flash the AIR BAG warning lamp seven times
^ Turn the warning lamp ON
^ Set DTC U1255 (Class 2 Initialization Error-IPC)
^ If the ignition is in the RUN position, has received at least one message from the SDM, and the IPC loses communication with the SDM, the IPC will set DTC U1096 and the SDM will set DTC U1096.

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. Intermittent Problems When a wire, connector or terminal repair is requested, use J 38125-A Terminal Repair Kit and refer to Wiring Repair.

Test Description
The numbers below refer to the step numbers on the diagnostic table:

2. This test determines if the SDM can communicate with the scan tool.
3. This test checks for sufficient BATTERY POSITIVE VOLTAGE voltage applied to the SDM.
5. This test determines whether the Serial Data Line Class 2 is malfunctioning.
6. This test checks for an open SDM Fuse.
7. This tests determines whether a short-to-ground caused the SDM Fuse to open.
8. This test determines whether the short-to-ground is due to a short in the wiring or internal to the SDM.
12. This test checks for a disconnected SDM.
18. This test checks for an open in the BATTERY POSITIVE VOLTAGE circuit.