Diesel Data: Automotive Repair

Supplemental Inflatable Restraint (SIR)









CIRCUIT DESCRIPTION

When the ignition switch is turned to "RUN," the SDM will perform tests to diagnose critical malfunctions within itself. Upon passing these tests "Ignition 1," 23 VLR and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. The SDM monitors the voltages at "Driver Side Low" terminal "3" and "Passenger Side Low" terminal "4" to detect shorts to be in the inflator module circuits.

DTC WILL SET WHEN

"Ignition 1" is in the normal operating voltage range. The voltage measured at both" Driver Side Low" and at "Passenger Side Low" are NOT below a specified value. Once these conditions are met and the voltage at "Driver Side Low" is above a specified value, DTC 25 will set. This test is run during "Turn-ON" tests and every 100 milliseconds during Continuous Monitoring."

ACTION TAKEN

SDM turns "ON" the "AIR BAG" warning lamp. sets a diagnostic trouble code.

DTC WILL CLEAR WHEN

The voltage measured at "Driver Side Low" is below a specified value for 500 milliseconds.

DTC CHART TEST DESCRIPTION

Numbers below refer to circled numbers on the diagnostic chart.

1. Monitoring "Driv. Senselo" may help to locate the fault. The value displayed by the TECH 1 is updated continuously so that intermittent shorts can be located by moving wires while monitoring "Driv. Senselo."

2. This test isolates the malfunction to one side of the driver inflator module yellow 2-way connector at the base of the steering column.

3. This test determines whether the malfunction is in CKT 347.

4. This test determines whether the malfunction is in CKT 348.

5. This test determines whether the malfunction is in the coil assembly or the driver inflator module.

DIAGNOSTIC AIDS

An intermittent condition is likely to be caused by a short to Be in the driver inflator module circuit. Inspect CKTs 347 and 348 carefully for cutting or chafing.