Test Notes

NORMAL OPERATION
A back-up power supply is contained within the air bag diagnostic monitor that consists of a capacitor and a voltage boost circuit. The voltage boost circuit charges the capacitor to approximately 24 volts (+\- 1 volt) when the ignition switch is turned to RUN. The back-up power supply is connected through a diode to diagnostic monitor Pin 15 (Circuit 611, W/O). The resistance of Circuit 611 (W/O) to ground is infinite since it is an open circuit.

This open circuit allows the capacitor to maintain its higher voltage because there is no discharge path for the capacitor. The air bag diagnostic monitor measures the voltage on the back-up power supply capacitor. If the voltage on the capacitor does not reach and maintain a minimum of 23 volts after approximately 45 seconds, the air bag diagnostic monitor will flash code 52 to indicate low voltage in the back-up power supply voltage boost circuit.


POSSIBLE CAUSES

Low Back-Up Power Supply Voltage Can Be Caused By:

1. Resistance on Circuit 611 (W/O) or Circuit 612 (P/O) to ground. Resistance to ground on Circuit 611 (W/O) or Circuit 612 (P/O) will cause the back-up power supply capacitor to discharge and the boost circuit will not be able to boost the voltage.

2. Boost circuit failure within the air bag diagnostic monitor. If the voltage boost circuit in the air bag diagnostic monitor is damaged, it will not be able to raise the back-up power supply voltage on the capacitor.