Supplemental Inflatable Restraint (SIR)

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, 23 VLR and the deployment loop voltages to make sure they are within their respective normal voltage ranges. Then the inflatable restraint control module proceeds to CONTINUOUS MONITORING. The inflatable restraint control module contains a resistor network connected to 5 volts, ground, and to the inflatable restraint control module sensor signal terminal 9. The 1.0 K ohms resistor in the inflatable restraint front end discriminating sensor parallel to the normally open switch provides a parallel path to ground. This causes a specified percentage of voltage to appear at the inflatable restraint control module sensor feed input. The inflatable restraint control module monitors this voltage to detect shorts to power or an open discriminating sensor.

CONDITIONS FOR SETTING THE DTC
^ The inflatable restraint control module is configured for a inflatable restraint front end discriminating sensor.
^ The voltage at SENSOR FEED terminal 9 is more than 5.0 volts for 500 milliseconds.

The CONTINUOUS MONITORING test checks for this DTC. This test occurs when IGNITION I 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 voltage at SENSOR FEED terminal 9 is less than 3.2 volts for 500 milliseconds.
^ History DTC
- You issue a scan tool CLEAR CODES command.
- Once 250 malfunction free ignition cycles have occurred.

DIANOSTIC AIDS
A broken or chafed wire in the inflatable restraint front end discriminating sensor circuit can cause an intermittent condition. Inspect CKT 349 and CKT 1751 carefully for cutting or chafing.

DTC TABLE TEST DESCRIPTION
Number(s) below refer to step number(s) on the diagnostic table.
2. This test checks for proper contact and/or corrosion of the yellow 2-way connector.
7. This test checks for a malfunctioning discriminating sensor.
8. This test checks for an open in CKT 1751.
11. This test isolates the open in CKT 1751 to one side of connector C114.
14. This test checks for proper contact and/or corrosion of the inflatable restraint control module connector.
19. This test checks for an open in CKT 349.
22. This test isolates the open in CKT 349 to one side of connector C114.
25. This test checks for a short to voltage in CKT 349.