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Home >> Mercury >> 1997 >> Grand Marquis V8-4.6L CNG SOHC VIN 9 >> Repair and Diagnosis >> Restraints and Safety Systems >> Air Bag Systems >> Testing and Inspection >> Diagnostic Trouble Code Tests and Associated Procedures >> B Code Charts >> DTC B1935: Passenger Air Bag Circuit Low Resistance/Shorted >> Test Notes

Test Notes

NORMAL OPERATION

NOTE: The air bag connector and the air bag diagnostic monitor harness connector have metal spring clips that act as shorting bars. These shorting bars are built into the plastic hard-shell connectors. The shorting bars are designed to short Circuits 607 (LB/O) and 616 (PK/BK) together when the connectors are not mated. Do not attempt to remove the air bag shorting bar and measure the resistance of the air bag module.

The shorting bar(s) in the air bag diagnostic monitor harness connector may be removed by removing the black spacer (locking wedge) from the connector. Use extreme caution when reinstalling the spacers to make sure they are installed correctly.

While the ignition switch is in the RUN position, the air bag diagnostic monitor runs periodic checks on the resistance of the driver and passenger air bag circuits.
- Normal resistance from Pin C277-5, Circuit 607 (LB/O) (passenger air bag feed) to Pin C277-4, Circuit 616 (PK/BK) (passenger air bag return) is between 0.9 ohm and 1.2 ohms.
- This resistance consists of the passenger air bag module resistance (approximately 1.0 ohm) plus a small amount of resistance due to the wire itself, crimps, etc.
- If the resistance across Pins C277-5, Circuit 607 (LB/O) and C277-4, Circuit 616 (PK/BK) is less than 0.7 ohm, the air bag diagnostic monitor will interpret this as a low resistance and the air bag diagnostic monitor will store in memory DTC B1935 and flash lamp fault code 35 on the AIR BAG indicator.
- If the low resistance is later serviced or otherwise rises into the normal range, a DTC B1935 will be stored in memory.

POSSIBLE CAUSES
Low resistance across Pins C277-5, Circuit 607 (LB/O) and C277-4, Circuit 616 (PK/BK) can be caused by:
- a poorly mated air bag connector or air bag diagnostic monitor harness connector which may not push the shorting bars back into their fully retracted position.
- a damaged or worn shorting bar which may short Circuit 607 (LB/O) and 616 (PK/BK).
- a short in the harness wires between Circuits 607 (LB/O) and 616 (PK/BK).
- a short circuit or low resistance in the passenger side air bag module. Do not attempt a direct resistance measurement of the air bag module. Follow the diagnostic procedure to determine if the air bag module resistance is lower than normal.
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