Supplemental Inflatable Restraint (SIR)

CIRCUIT DESCRIPTION
The DERM measures the deployment loop energy reserve voltage ("36 VLR") and checks that it has reached a certain voltage within 7 seconds after "Ignition 1" is applied. If this voltage is not reached DTC 41 is set. The DERM monitors the "36 VLR" and checks that it remains above a certain voltage while "Ignition 1" voltage is present. If the "36 VLR" falls below a certain voltage after initial charging DTC 42 is set. These diagnostic trouble codes indicate a malfunction internal to the DERM or a short to ground or B+ between the diode attached to terminal "B" of the arming sensor and the "36 VLR" output terminal "A2".

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

FAILURE CONDITIONS
DTC 41 will set if the "36 VLR" has not reached a certain voltage 7 seconds after "Turn-ON." DTC 42 will set if the "36 VLR" is below a certain voltage after initial charging.

ACTION TAKEN
DERM turns "ON" the "INFL REST" warning lamp.

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

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks whether the DERM has set the diagnostic trouble code falsely.
2. This test determines whether the malfunction is due to a short in the arming sensor or a short from the "36 VLR" circuit to B+.