B1121

Circuit Description
When you first turn the ignition switch to the RUN position, the Inflatable Restraint Sensing and Diagnostic Module (SDM) performs tests in order to diagnose critical malfunctions within the module. The SDM measures the ignition positive voltage and the deployment loop voltages in order to ensure that the voltages are within their respective normal voltage ranges. The SDM proceeds using the RESISTANCE MEASUREMENT test. During one portion of the RESISTANCE MEASUREMENT test, the SDM does the following functions:
^ Grounds the DRIVER FRONTAL LOW terminal 9 through an internal current sink.
^ Connects the DRIVER FRONTAL HIGH terminal 10 to an internal constant current source. This current produces proportional voltage drops in the deployment loop.
^ Measures the voltage difference between the DRIVER FRONTAL HIGH and the DRIVER FRONTAL LOW.
^ Calculates the resistance of the driver frontal deployment loop using the measured voltage.

Conditions for Setting the DTC
^ The driver and passenger frontal deployment loops are not open.
^ The driver and passenger frontal deployment loops are not shorted to voltage.
^ The driver and passenger frontal deployment loops are not shorted to ground.
^ The driver frontal deployment loop resistance is more than 3.8 Ohms. The driver frontal deployment loop consists of the following components:
- Inflatable Restraint Steering Wheel Module.
- Inflatable Restraint Steering Wheel Module Coil.
- Harness wiring of circuit 347.
- Harness wiring of circuit 348.
- Connector terminal contact.

The RESISTANCE MEASUREMENT test inspects for this malfunction. This test only occurs once each ignition cycle when the ignition positive voltage is within the normal operating voltage range.

Action Taken When the DTC Sets
^ The SDM sets a diagnostic trouble code.
^ The SDM commands the instrument panel cluster (IPC) to turn ON the AIR BAG warning lamp.

Conditions for Clearing the MIL/DTC
The DTC will clear when one of the following conditions is met:
^ Current DTC
The resistance of the driver frontal deployment loop is less than 3.8 Ohms and the ignition switch is cycled.
^ History DTC
- You issue a scan tool CLEAR CODES command.
- 250 malfunction free ignition cycles have occur.

When you issue a scan tool CLEAR CODES command and the malfunction is still present, the DTC will not reappear until the next ignition cycle.

Diagnostic Aids
A poor connection can cause an intermittent condition.

Inspect the following items for a poor connection:
^ The Inflatable Restraint Steering Wheel Module steering column connector terminals A and B.
^ The upper Inflatable Restraint Steering Wheel Module Coil connector terminals A and B.
^ The SDM terminals 10 and 9.
^ The wire to terminal connections in circuit 347.
^ The wire to terminal connections in circuit 348.

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-B Terminal Repair kit and refer to Wiring Repair. Intermittents and Poor Connections

Test Description
The numbers below refer to the step numbers on the diagnostic table:
2. This test checks for proper contact or corrosion of the yellow 2-way connector.
9. This test isolates the malfunction to one side of the Inflatable Restraint Steering Wheel Module yellow 2-way connector.
10. This test determines whether the malfunction is due to the Inflatable Restraint Steering Wheel Module or the module coil.
13. This test checks for proper contact or corrosion of the SDM connector.
18. This test determines whether the malfunction is in circuit 347.
20. This test determines whether the malfunction is in circuit 348.