Supplemental Inflatable Restraint (SIR)

CIRCUIT DESCRIPTION
The DERM measures the deployment loop energy reserve voltage ("36 VLR" circuit) and checks that it has reached a certain voltage within seven seconds after "Ignition 1" voltage is applied to the DERM. If this voltage is not reached, DTC 41 is set. The DERM monitors the "36 VLR" output, terminal "A2," and checks that it remains above a certain voltage while "Ignition 1" voltage is present at the DERM. If the "36 VLR" output voltage falls below a certain voltage after initial charging, DTC 42 is set. These two DTCs indicate a fault internal to the DERM or a short to B+ between the arming sensor and the DERM (CKT 236).

TEST CONDITIONS
DTC 41 is tested for once each ignition cycle during the "Turn-ON Tests." DTC 42 is tested for every 100 milliseconds during the "Continuous Monitoring Tests."

FAILURE CONDITIONS
DTC 41 will set if the "36 VLR" output voltage has not reached a certain voltage seven seconds after "Ignition 1" voltage is applied to the DERM. DTC 42 will set if the "36 VLR" output voltage is below a certain voltage after initial charging.

ACTION TAKEN
The DERM illuminates the "INFL REST" indicator.

CONDITIONS TO CLEAR
DTC 41 will clear each time the ignition switch is turned to "OFF." DTC 42 will clear if the "36 VLR" output voltage is greater than a certain voltage for 500 milliseconds after it has been set.

TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks for a faulty arming sensor.
2. This test determines whether the fault is due to a short to B+ in the "36 VLR" CKT 236 or a faulty DERM.