Who knows airbag codes?

[exbass94]

I tried asking this on another forum but got no help. I figure my chances are better here since we have some Ford techs.

I recently bought a 1994 Ford Bronco as a project truck. Yesterday I replaced the clock spring because the horn didn't work, airbag light was flashing, and cruise buttons didn't work. So now the new clock spring is installed, the horn now works, I didn't test the cruise control yet, and the airbag light still flashes after the ignition is on for about 45 seconds. It's flashing a code 52, which apparently means "backup power supply -- voltage boost fault."

I can't figure out how to fix it. I found the following instructions online, but some parts are not clear to me:

PINPOINT TEST DTC 52: BACKUP POWER SUPPLY -- VOLTAGE BOOST FAULT


Normal Operation

A backup 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 lock cylinder is turned to ON. The backup power supply is connected through a diode to air bag diagnostic monitor Pin 15 (Circuit 611, W/O). The resistance of Circuit 611 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 backup 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 backup power supply voltage boost circuit.

Possible Causes
Low backup power supply voltage can be caused by:
1. Resistance in Circuit 611 (W/O) to ground. Resistance to ground on Circuit 611 or Circuit 612 (P/O) will cause the backup power supply capacitors 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 faulty it is unable to raise the backup power supply voltage on the capacitor.


Pinpoint Tests

PINPOINT TEST DTC 52: BACKUP POWER SUPPLY -- VOLTAGE BOOST FAULT
52-1 CHECK FOR DTC 52

l Turn ignition switch lock cylinder to ON.

l Count diagnostic trouble code (if any).

l Is Code 52 flashing?

Yes
GO to «52-2».

No
READ the normal operation description for this diagnostic trouble code. EXAMINE the diagnostic trouble code schematic and LOOK for areas where intermittent problems would occur (connectors, splices, crimps, etc.). DO NOT PROCEED with pinpoint tests until the code is flashing! Failure to do so will result in needless replacement of the air bag diagnostic monitor and repeat service.



Pinpoint Tests

PINPOINT TEST DTC 52: BACKUP POWER SUPPLY -- VOLTAGE BOOST FAULT


52-2 DEACTIVATE SYSTEM


l Deactivate system.

l Turn ignition switch lock cylinder from OFF to RUN.

l Wait 45 seconds.

l Measure voltage between Pin 15 (Circuit 611 (W/O) and Pin 3 (ground).

l Is the voltage measured 24 volts ± 1 volt?

Yes
REPLACE air bag diagnostic monitor. RECONNECT system. VERIFY system. REACTIVATE system.

No
GO to «52-3».


Pinpoint Tests

PINPOINT TEST DTC 52: BACKUP POWER SUPPLY -- VOLTAGE BOOST FAULT


52-3 CHECK FOR OPEN IN CIRCUIT 611


l Turn ignition switch lock cylinder OFF.

l Disconnect air bag diagnostic monitor.

l Set Rotunda Dwell-Tach-Volts Ohms Tester 059-00010 or equivalent on 200,000 or auto scale.

l Measure resistance of Pin 15 -- Circuit 611 (W/O) to Pin 3 (ground).

l Is the resistance measured infinite (open)?

Yes
REPLACE air bag diagnostic monitor. RECONNECT system. VERIFY system. REACTIVATE system.

No
GO to «52-4».


Pinpoint Tests

PINPOINT TEST DTC 52: BACKUP POWER SUPPLY -- VOLTAGE BOOST FAULT


52-4 MEASURE RESISTANCE OF CIRCUIT 611


l Disconnect 5-wire safing sensor.

l Measure resistance between Pin 15 (Circuit 611, W/O) and Pin 3 (ground).

l Is the resistance measured greater than 100,000 ohms?

Yes
GO to «52-5».

No
LOCATE and SERVICE the short to ground in Circuit 611, W/O. RECONNECT system. VERIFY system. REACTIVATE system.


Pinpoint Tests

PINPOINT TEST DTC 52: BACKUP POWER SUPPLY -- VOLTAGE BOOST FAULT


52-5 CHECK FOR SHORT IN SENSOR


l Measure resistance of W/O wire in safing sensor connector to sheet metal ground.

l Is the resistance measured greater than 100,000 ohms?

Yes
LOCATE and SERVICE the short to ground in Circuit 612 (P/O). RECONNECT system. VERIFY system. REACTIVATE system.

No
REPLACE safing sensor. RECONNECT system. VERIFY system. REACTIVATE system.

The instructions say to "deactivate the system" and then turn ignition switch to run. How do I deactivate the system?
When it says to measure voltage between pins, does that mean I disconnect the wire harness to the module and probe the harness, or do I probe the pins on the module? Do I do this with the battery connected or disconnected? Everyone always says disconnect the battery before messing with the airbag system but if it's disconnected, wouldn't I get 0 volts no matter what?

 

[adsm08]

Deactivation of the system is usually done by pulling the fuse for the module. Since the booster is. Capacitor in the module I would test voltage at the module. Battery connected.

FWIW I rarely bother to deactivate the system and have yet to set one off working on it.

Postin' from teh Galaxy