Test Notes

Air Bag Diagnostic Monitor Typical Pin Voltages With System Connected And Engine Running:

NORMAL OPERATION
The air bag diagnostic monitor measures the voltage at Pins C277-2, C277-3, C277-4 and C277-5 of the air bag diagnostic monitor connector. The voltage at these pins is set by the air bag diagnostic monitor and varies with charging system voltage (the expected voltages are shown in the table provided). If the air bag diagnostic monitor detects low voltage on any of these pins, the air bag diagnostic monitor will store in memory DTC B1913 and flash lamp fault code 13 on the AIR BAG indicator to indicate a possible short to ground on these circuits.

At the same time the air bag diagnostic monitor begins flashing lamp fault code 13, it attempts to disarm the air bag system to prevent inadvertent deployment of the air bag(s) by opening the Fuse 10 (10 A) fuse feeding air bag diagnostic monitor Pins C277-13 and C277-14. It attempts to open the fuse by activating a solid state switch which shorts the battery feed at Pin C277-13, Circuit 937 (R/W) to sheet metal ground at the air bag diagnostic monitor's bracket.

The air bag diagnostic monitor will make up to three attempts to open this fuse, spaced one minute apart.
- If the air bag diagnostic monitor has opened the fuel and thus removed battery positive voltage (B+) at Pin C277-14, a DTC B1867 will be stored (refer to DTC B1867, Normal Operation, for further details).
- If the air bag diagnostic monitor attempts to open the 10 A fuse three times and fails each time, a DTC B1924 will be stored (refer to Pinpoint Test A, Normal Operation, for further details).
- After the 10 A fuse is opened or three attempts to open it fail, the air bag diagnostic monitor will not attempt to disarm again until the DTC B1913 has been serviced and cleared by performing DTC B1913.
- Should the short on Pins C277-2, C277-3, C277-4 and C277-5 be intermittent or repaired, the air bag diagnostic monitor will flash a lamp fault code 53 (or a higher priority DTC such as lamp fault code 12 if one exists) on the next ignition switch cycle.


POSSIBLE CAUSES

WARNING: Servicing a Lamp Fault Code 13 (DTC B1913) will usually occur after servicing of a Lamp Fault Code 12 (DTC B1867) has been completed. under no circumstances substitute another fuse value for the 10 A fuse. Any fuse other than 10 A may cause disarming failure and may result in danger to the occupants of the vehicle. Do not attempt to replace the 10 A fuse unless the air bag system first has been deactivated.


Low voltage at air bag diagnostic monitor Pins C277-2, C277-3, C277-4 or C277-5 can be caused by:
- a short to ground on Circuits 607 (LB/O), 614 (GY/O), 615 (GY/W) or 616 (PK/BK), causing the diagnostic voltage to drop.
- resistance to ground on Circuits 617 (PK/O), 619 (PK/W), 624 (Y/W), 625 (Y/LG) or internal resistance to ground In either of the primary crash sensors may activate an air bag diagnostic monitor circuit which may cause the voltage to drop.
- an internal short to ground within the air bag sliding contact, causing the driver side air bag circuit(s) to be shorted to ground.
- an internal short to ground within the driver side air bag module or passenger side air bag module.