Supplemental Inflatable Restraint (SIR)

Description:

CIRCUIT DESCRIPTION
When you first turn the ignition switch to the RUN position the inflatable restraint control module performs tests to diagnose critical malfunctions within itself. Next the inflatable restraint control module measures IGNITION 1 and the deployment loop voltages to make sure they are within their respective normal voltage ranges. Then the inflatable restraint control module proceeds with the RESISTANCE MEASUREMENT test. During one portion of the RESISTANCE MEASUREMENT test, the inflatable restraint control module does the following:
^ Grounds the DRIVER SIDE LOW terminal 3 through an internal current sink.
^ Connects the DRIVER SIDE HIGH terminal 2 to an internal constant current source. This current produces proportional voltage drops in the deployment loop.
^ Measures the voltage difference between DRIVER SIDE HIGH and DRIVER SIDE LOW.
^ Calculates the resistance of the driver deployment loop using the measured voltage.

CONDITIONS FOR SETTING THE DTC
^ The driver and passenger deployment loops are not open.
^ The driver and passenger deployment loops are not shorted to voltage.
^ The driver deployment loop is not shorted to ground.
^ The driver deployment loop resistance is less than 1.7 ohms. The driver deployment loop consists of the following components:
- Inflatable restraint steering wheel module.
- Inflatable restraint steering wheel module coil.
- Harness wiring of CKT 347.
- Harness wiring of CKT 348.
- Connector terminal contact.

The RESISTANCE MEASUREMENT test checks for this malfunction. This test only occurs once each ignition cycle when IGNITION 1 is within the normal operating voltage range.

ACTION TAKEN WHEN THE DTC SETS
^ The inflatable restraint control module sets a diagnostic trouble code.
^ The inflatable restraint control module turns,ON the AIR BAG warning lamp.

CONDITIONS FOR CLEARING THE DTC
^ Current DTC
- The resistance of the driver deployment loop is more than 1.7 ohms and the ignition switch is cycled.
^ History DTC
- You issue a scan tool CLEAR CODES command.
- Once 250 malfunction free ignition cycles have occurred.

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
The following can cause an intermittent condition:
^ A short circuit between CKT 347 and CKT 348.
^ A short circuit between CKT 347 and CKT 1403.
^ A short circuit between CKT 347 and CKT 1404.
^ A malfunctioning shorting bar on the inflatable restraint steering wheel module connector.
^ A malfunctioning shorting bar on the inflatable restraint steering wheel module coil steering column connector.

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

DTC TABLE TEST DESCRIPTION
Number(s) below refer to step number(s) on the diagnostic table.
2. This test determines the deployment loop resistance measured by the inflatable restraint control module.
6. This test isolates the malfunction to one side of the inflatable restraint steering wheel module coil yellow 2-way connector located near the case of the steering column.
7. This test determines whether the malfunction is in the inflatable restraint steering wheel module CKT or the inflatable restraint steering wheel module.
10. This test checks for a short from CKT 47 to CKT 348.
12. This test checks for a short from CKT 347 to CKT 1404.