Test Notes

NORMAL OPERATION

Charging System Voltage:

The air bag diagnostic monitor measures the voltage at Pins C276-23, Circuit 625 (Y/LG) and C276-24, Circuit 624 (Y/W) of the air bag diagnostic monitor connector. The voltage at these pins varies with charging system voltage (the expected voltages are shown in the table). If the air bag diagnostic monitor measures a voltage of less than five volts on either of these pins, the air bag diagnostic monitor will store in memory Diagnostic Trouble Code (DTC) B1914 and flash Lamp Fault Code (LFC) 14 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 14, it attempts to disarm the air bag system to prevent inadvertent deployment of the air bag(s) by blowing the battery fuse 18 (10A) feeding air bag diagnostic monitor Pins C277-13, Circuit 937 (R/W) and C277-14, Circuit 937 (R/W). It attempts to blow the fuse by activating an internal 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 blow this fuse, spaced at one minute apart.
- If the air bag diagnostic monitor has blown the fuse and thus removed battery voltage at Pin C277-14, Circuit 937 (R/W), a DTC B1867 will be stored (refer to Pinpoint Test A : System Disarm Failure or Internal Diagnostic Monitor Fault / Test Notes for further details).
- If the air bag diagnostic monitor attempts to blow the 10A battery fuse three times and fails each time, a DTC B1924 will be stored (refer to Pinpoint Test A : System Disarm Failure or Internal Diagnostic Monitor Fault / Test Notes for further details).
- After the 10A fuse is blown or three attempts to blow it fail, the air bag diagnostic monitor will not attempt to disarm again until the DTC B1914 has been serviced and cleared by performing DTC B1914 diagnostic procedures.
- Should the short on Pins C276-23 and C276-24 be intermittent or repaired, the air bag diagnostic monitor will flash lamp fault code 54 (or a higher priority DTC such as lamp fault code 12 if one exists) on the next ignition switch cycle.

POSSIBLE CAUSES

WARNING: Servicing lamp fault code 14 (DTC B1914) will usually occur after servicing of lamp fault code 12 (DTC B1867) has been completed. Under no circumstances substitute another fuse value for the 10A battery fuse. Any fuse other than 10a may cause disarming failure and may result in danger to the occupants of the vehicle. Do not attempt to replace the 10A battery fuse unless the air bag system first has been deactivated.


Low voltage at diagnostic monitor Pins C276-23, C277-15, C277-16 or C276-24 can be caused by:
- a short to ground on Circuits 617 (PK/O), 619 (PK/W), 624 (Y/W), or 625 (Y/LG) causing the diagnostic voltage to drop.
- an internal short to case ground within either of the primary crash sensors.