Mustang 1990-1991 Air Bag Diagnostic Codes and Debug Information.

Use the information at your own risk. There is no claim to accuracy.

1. Are all crash sensors connected and mounted to the vehicle?
   


2. Is black 3-way connector at base of steering column connected?
   


3. Are the air bags or air bag simulators connected?
   


4. Is air bag diagnostic monitor (14B056) connected?
   


5. Is vehicle battery connected?
   

1. LH Radiator Primary Crash Front Air Bag Sensor and Bracket (14B005) -- LH side of radiator support.
   


2. RH Radiator Primary Crash Front Air Bag Sensor and Bracket (14B004) -- RH side of radiator support.
   


3. Safing Sensor -- Integral with air bag diagnostic monitor (14B056).
   


4. Driver Side Air Bag Module (043B13) -- Steering wheel (3600).
   


5. Passenger Side Air Bag Module (044A74) -- Above glove compartment (06010).
   


6. Air Bag Sliding Contact (14A664) -- Behind steering wheel.
   


7. Air Bag Diagnostic Monitor and Bracket -- In center console behind climate controls.
   

1. Disconnect battery ground cable (14301).



2. WARNING: THE BACK-UP POWER SUPPLY ENERGY MUST BE DEPLETED BEFORE ANY AIR BAG COMPONENT SERVICE IS PERFORMED. TO DEPLETE BACK-UP POWER SUPPLY ENERGY, DISCONNECT THE NEGATIVE BATTERY CABLE AND WAIT 20 MINUTE TO AVOID ACCIDENTAL DEPLOYMENT AND POSSIBLE PERSONAL INJURY.
   Wait 20 MINUTES . This is the time required for back-up power supply in air bag diagnostic monitor to deplete its stored energy.
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3. WARNING: PLACE AIR BAG MODULE ON BENCH WITH TRIM COVER FACING UP TO AVOID POSSIBLE PERSONAL INJURY.
   Remove two back cover plugs and remove screw and washer assemblies retaining driver side air bag module (043B13) to steering wheel (3600). Disconnect driver air bag connector. Remove driver side air bag module from vehicle.
   Connect Rotunda Air Bag Simulator 105-00010 or equivalent to vehicle harness at top of steering column.


4. Remove passenger side air bag module (044A74) as outlined. Install Rotunda Air Bag Simulator 105-00010 or equivalent on vehicle harness connector in place of passenger side air bag module.


5. Reconnect battery ground cable.

1. An open circuit, preventing battery voltage from reaching pin 13 and the backup power supply.
   NOTE: If the instrument panel fuse and/or the power distribution fuse are blown, be sure to diagnose the system for Possible Causes 2 and 3 below.
   
   
2. A short to ground in the battery feed circuit or the circuits 611 (W/O) and 612 (P/O) may result in a blown instrument panel fuse and/or the power distribution fuse.
   
   
3. An internal short to ground within the safing sensor may result in a blown instrument panel fuse and/or distribution fuse.
   
   
4. A disconnected or poorly connected backup power supply may cause low voltage on pin 14 of the diagnostic monitor. 1989 vehicles without a backup power supply have an additional wire on pin 14 of the diagnostic monitor that is connected to battery voltage.
   
   
5. A problem in the charging system causing battery and backup power supply voltage to drop below nine volts.

1. An open circuit or high resistance in the wiring harness in circuit 614 (GY/O) or 623 (P/W).



2. An open circuit or high resistance inside the safing sensor across the GY/O and P/W wires.

1. Resistance to ground on circuit 614 or 623. Circuits 614 and 623 should be open circuits to ground when the diagnostic monitor is disconnected from the harness. Resistance to ground on these circuits can cause a drop in the diagnostic voltage on both circuits.



2. Low resistance in one or more of the primary crash sensors. If the resistance of one or more of the primary crash sensors is lower than normal, the voltage on pin 11 will be pulled down too low,



3. A poor ground on pin 3 of the diagnostic monitor may cause voltage to appear on the diagnostic monitor ground reference. Any voltage on the ground reference will cause the diagnostic monitor to measure the voltage at pin 11 as low, even though the voltage at pin 11 with respect to the sheet metal is normal.



4. Intermittent battery voltage at pin 13 can cause the reference voltage inside the diagnostic monitor to fluctuate and cause Fault Code 4 in some circumstances.

1. A poor connection due to loose mounting, dirt or corrosion at the safing sensor mounting surface.



2. An open or damaged wire in circuit 613 (DB/W) from pin 16 of the diagnostic monitor connector to the safing sensor.



3. An open wire or loose rivet inside the safing sensor.

1. An open circuit or high resistance in the wiring harness in circuit 611 (W/O) or 612 (P/O).



2. An open or high resistance inside the safing sensor across the W/O and P/O wires.

1. A short in the wiring harness between circuit 614 (GY/O) or 623 (P/W) and another wire. This can cause high voltage in these circuits.
   NOTE: The wiring leading to the safing sensor(s) has higher voltage wires bundled in the harness with circuits 614 and 623.



2. A short in the clockspring between circuit 614 and some horn or speed control wiring.



3. A short across the normally open contacts of the safing sensor(s).
   NOTE: The voltage on circuits 611 and 612 inside the safing sensor(s) is usually battery voltage. There should be an open circuit across the contacts of the safing sensor(s) if the sensor(s) is operating normally. If either of the sensor contacts are closed, the voltage on circuit 614 would be high (battery voltage).

1. Primary Sensor #1 - Diagnostic Monitor Pin 20 (Circuit 618 P/LG).
2. Primary Sensor #2 - Diagnostic Monitor Pin 21 (Circuit 620 P/LB).
3. Primary Sensor #3 - Diagnostic Monitor Pin 22 (Circuit 622 T/BK).

1. A poor ground connection due to loose mounting, dirt, or corrosion at the primary crash sensor mounting location.



2. An open or damaged wire in circuits 618 (P/LG), 620 (P/LB), 622 (T/BK), somewhere between pin 20, 21, 22 and one or more of the primary crash sensors.



3. An open wire or loose wire attachment inside a primary crash sensor.

1. Inspect wiring and harness in the areas where they pass through or are located next to metal components (i.e. engine compartment bulkhead, body sheet metal, component mounting brackets, etc.).

PINPOINT TEST C1: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C1    DEACTIVATE SYSTEM


   o  Deactivate system.

   o  Disconnect diagnostic monitor.

   o  Measure voltage from diagnostic monitor connector Pin 13 (+)
      (Circuit 937, R/W) to PIn 2 (-) (57, BK).

   o  Is voltage greater than 10 volts?

      Yes
         REPLACE diagnostic monitor. VERIFY system. REACTIVATE system.

      No
         GO to .





PINPOINT TEST C2: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C2    CHECK INSTRUMENT PANEL FUSE


   o  Check instrument panel fuse No. 7, 15 amp.

   o  Is fuse open?

      Yes
         GO to .

      No
         GO to .






PINPOINT TEST C3: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C3    CHECK FOR SHORT TO GROUND IN CIRCUIT 937 (R/W)


   o  Measure resistance from diagnostic monitor connector Pin 13 (Circuit
      937, R/W) to ground.

   o  Is resistance less than 10 ohms?

      Yes
         LOCATE and SERVICE short to ground in Circuit 937 (R/W). REPLACE
         open fuse. RECONNECT system. VERIFY system. REACTIVATE system.

      No
         GO to .




PINPOINT TEST C4: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C4    CHECK FOR SHORT TO GROUND IN CIRCUIT 611 (W/O)


   o  Measure resistance from diagnostic monitor connector Pin 15 (Circuit
      611, W/O) to ground.

   o  Is resistance less than 10 ohms?

      Yes
         GO to .

      No
         GO to .




PINPOINT TEST C5: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C5    CHECK FOR SHORT TO GROUND IN LH B-PILLAR PANEL SAFING SENSOR


   o  Disconnect LH B-pillar safing sensor.

   o  Measure resistance from diagnostic monitor connector Pin 15 (Circuit
      612, P/O) to ground.

   o  Is resistance less than 10 ohms?

      Yes
         LOCATE and SERVICE short to ground in Circuit 611 (W/O). REPLACE
         open fuse. RECONNECT system. VERIFY system. REACTIVATE system.

      No
         GO to .





PINPOINT TEST C6: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C6    CHECK FOR SHORT TO GROUND IN CIRCUIT 612 (P/O)


   o  Measure resistance from diagnostic monitor connector Pin 23 (Circuit
      612, P/O) to ground.

   o  Is resistance less than 10 ohms?

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

      No
         GO to .





PINPOINT TEST C7: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C7    VERIFY SHORT TO GROUND IN LH B-PILLAR SAFING SENSOR


   o  Measure resistance from LH B-pillar safing sensor connector Circuit
      611 (W/O) and Circuit 612 (P/O) to ground.

   o  Is resistance less than 10 ohms for either circuit?

      Yes
         REPLACE LH B-pillar safing sensor. REPLACE open fuse. RECONNECT
         system. VERIFY system. REACTIVATE system.

      No
         INSPECT for crossed wires at LH B-pillar safing sensor connector
         and diagnostic monitor connector. SERVICE Circuit 611 (W/O)
         and/or Circuit 612 (P/O). REPLACE open fuse/fusible link.
         REACTIVATE system.




PINPOINT TEST C8: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C8    CHECK FOR INTERMITTENT SHORT TO GROUND


   o  Replace open fuse.

   o  Reconnect diagnostic monitor.

   o  Did fuse open again?

      Yes
         REPLACE Diagnostic monitor. REPLACE open fuse. VERIFY system.
         REACTIVATE system.

      No
         INSPECT intermittent short to ground in Circuits 937 (R/W), 611
         (W/O) and 612 (P/O). SERVICE circuits as required. RECONNECT
         system. VERIFY system. REACTIVATE system.






PINPOINT TEST C9: FAULT INDICATION--AIR BAG INDICATOR FLASHES FAULT CODE
10--PROBABLE FAULT--LOSS OF BATTERY POWER TO AIR BAG FIRING CIRCUIT


 C9    CHECK FOR PROPER BATTERY VOLTAGE


   o  Measure voltage of vehicle battery.

   o  Is voltage less than 10 volts?

      Yes
         RECHARGE vehicle battery. RECONNECT system. VERIFY system.
         REACTIVATE system.

      No
         LOCATE and SERVICE open in Circuit(s) 937 (R/W) and/or 38 (BK/O).
         RECONNECT system. VERIFY system. REACTIVATE system.