Source Voltage Drop

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Description

The air bag sensor assembly is equipped with a voltage-increase circuit to allow system operation in case source (battery) voltage drops below minimum. When battery voltage drops, voltage-increase circuit functions to increase voltage of air bag system to normal voltage.

The malfunction display for this circuit is different from other air bag system circuits. When source voltage drop is detected and no other DTCs are present, the AIR BAG warning light remains illuminated constantly. Source voltage drop is not recorded in air bag sensor assembly as a malfunction, and when source voltage returns to normal, AIR BAG warning light will turn off.

Diagnostic Procedure

1. Turn ignition switch to LOCK position. Disable air bag system. See DISABLING SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Reconnect negative battery cable.

2. Turn ignition switch to ON position. Turn on electrical accessories (defogger, wipers, headlights, blower motor, etc.). Measure voltage between ground and air bag sensor assembly connector A20, terminals No. 5 (circuit IG2, Black/Orange wire) and No. 6 (circuit IG1, Black/Red wire) independently. See Fig. 22 . Turn electrical accessories off. If voltage is 10-14 volts, go to next step. If voltage is not 10-14 volts, check harness between battery and air bag sensor assembly and check battery and charging system. See WIRING DIAGRAMS .

3. Turn ignition switch to LOCK position. Activate air bag system. See ACTIVATING SYSTEM under DISABLING & ACTIVATING AIR BAG SYSTEM. Turn ignition switch to ON position. Turn on electrical accessories again. If AIR BAG warning light goes out, system operation is normal at this time. If AIR BAG warning light does not go out, check for DTCs. See RETRIEVING CODES under DIAGNOSTICS. If DTC is displayed, go to appropriate DTC. If a normal code is displayed (2 flashes per second), replace air bag sensor assembly.

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