Section 01-20B: Restraints, Passive—Supplemental Air Bag System
1993 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Diagnostic Trouble Code 13

 

Air Bag Or Crash Sensor Circuit Shorted To Ground

 

Normal Operation

The diagnostic monitor measures the voltage at Pin 11 (Circuit 614, GY/O) of the diagnostic monitor connector. The voltage at Pin 11 varies with charging system voltage (the expected voltage at Pin 11 is shown in the chart below). Note that Circuit 614 is connected to Circuit 615 (GY/W) through the driver side air bag. Also, note that Circuit 615 is connected to the primary crash sensor feed circuits (617 (PK/O), 619 (PK/W) and 621, W/Y) through a diode inside the diagnostic monitor. If the diagnostic monitor measures a voltage of 2.0 volts or less at Pin 11, the monitor will flash out Diagnostic Trouble Code 13 to indicate a possible short to ground on this circuit ( refer to Possible Causes for additional circuits that may be shorted to ground). When flashing Diagnostic Trouble Code 13, the diagnostic monitor blows its internal thermal fuse. This disables the air bag deployment circuit. If the voltage at Pin 11 returns to normal, a Diagnostic Trouble Code 51 will be present due to the open thermal fuse (refer to Diagnostic Trouble Code 51 as outlined).

NOTE: Diagnostic Trouble Code 13 will flash only while the short to ground is present.

 

Possible Causes

Low voltage at diagnostic monitor Pin 11 can be caused by:

  1. A short to ground within the wiring harness on Circuits 614 (GY/O), 615 (GY/W), 623 (P/W), 617 (PK/O), 619 (PK/W), or 621 (W/Y) causing the diagnostic voltage to drop.
  1. An internal short to ground within the clockspring assembly causing the driver side air bag circuit(s) to be shorted to ground.
  1. An internal short to ground within the safing sensor causing Circuit 614 (GY/O) or 623 (P/W) to be shorted to ground.
  1. An internal short to ground within one or more of the crash sensors causing Circuits 617 (PK/O), 619 (PK/W) and 621 (W/Y) to be shorted to ground.
  1. An internal short to case ground within the driver side air bag.

    NOTE: Circuits 617 (PK/O), 619 (PK/W) and 621 (W/Y) are all connected together inside the diagnostic monitor. Therefore, a short to ground on any of these circuits will short all of the circuits to ground.



    CHARGING SYSTEM VOLTAGE
    Charging System Voltage Voltage at PIN NO. 11
    9.0 1.9
    9.5 2.0
    10.0 2.1
    10.5 2.2
    11.0 2.3
    11.5 2.4
    12.0 2.5
    12.5 2.6
    13.0 2.7
    13.5 2.7
    14.0 2.9
    14.5 3.0
    15.0 3.1
    15.5 3.2
    16.0 3.3



Electrical Schematic—Diagnostic Trouble Code 13




 

DIAGNOSTIC TROUBLE CODE 13

 

13-1 VERIFY CONDITION

Yes
GO to 13-2.

No
Read the normal operation description for this diagnostic trouble code. EXAMINE the diagnostic trouble code schematic and look for areas where intermittent conditions would occur (connectors, splices, crimps, etc.)
DO NOT proceed with pinpoint test until the code is flashing!
Failure to do so will result in needless replacement of the air bag system components and repeat service.

 

13-2 DEACTIVATE SYSTEM

NOTE: Never attempt to replace diagnostic monitor with a diagnostic trouble code 13 present, unless instructed to do so.

Yes
GO to 13-5.

No
GO to 13-3.

 

13-3 CHECK AIR BAG(S) AND CLOCKSPRING

  • Inspect clockspring wiring in steering wheel and driver air bag for damaged, chafed, or pinched wires.
  • Are any component wires damaged?
Yes
REPLACE component(s) which have damaged wires. GO to Diagnostic Trouble Code 51 .

No
GO to 13-4.

 

13-4 VERIFY SHORT IN AIR BAG(S)

  • Make sure that the shorting bars are correctly installed in the driver air bag connectors.

     WARNING: USE A HANDHELD DIGITAL OHMMETER WITH LESS THAN 10 MA SHORT-CIRCUIT CURRENT ON THE LOWEST RESISTANCE SCALE POSSIBLE (TYPICALLY 2000 OHM SETTING). FAILURE TO USE A METER OF THIS TYPE MAY CAUSE PERSONAL INJURY DUE TO AIR BAG DEPLOYMENT.

  • Measure the resistance between either of the terminals in the air bag connector and the metal case of the driver air bag assembly.
  • Is the resistance reading infinite (open)?
Yes
REPLACE clockspring. GO to Diagnostic Trouble Code 51.

No
REPLACE the driver air bag assembly. GO to Diagnostic Trouble Code 51.

 

13-5 INSTALL AIR BAG SIMULATOR AT BASE OF STEERING COLUMN

  • Remove driver air bag simulator.
  • Disconnect black 3-way connector containing Circuits 614 (GY/O) and 615 (GY/W) at base of steering column.
  • Install air bag simulator on vehicle harness side at base of steering column.
  • Verify system.
  • Does air bag indicator flash a diagnostic trouble code 13?
Yes
GO to 13-6.

No
REPLACE clockspring. GO to Diagnostic Trouble Code 51.

 

13-6 REMOVE AIR BAG SIMULATOR FROM BASE OF STEERING COLUMN

  • Remove air bag simulator from vehicle harness connector at base of steering column.
  • Verify system.
  • Does air bag indicator flash a diagnostic trouble code 13?
Yes
GO to 13-7.

No
LOCATE and SERVICE short to ground in wiring harness Circuit 615 (GY/W). GO to Diagnostic Trouble Code 51.

 

13-7 CHECK FOR SHORTED WIRING

  • Turn key off.
  • Disconnect diagnostic monitor.
  • Measure resistance from diagnostic monitor connector Pin 17 (Circuit 617, PK/O), Pin 18 (Circuit 618, PK/W), Pin 19 (Circuit 621, W/Y) and Pin 11 (Circuit 614, GY/O) to ground. Normal resistance to ground on these pins are as follows:
    • Pin 11 - Open (infinite)
    • Pin 17 - 1180 ohms ± 20 ohms
    • Pin 18 - 1180 ohms ± 20 ohms
    • Pin 19 - 1180 ohms ± 20 ohms
  • Are any of these circuits shorted to ground?




Yes
If Pin 11 is shorted to ground, GO to 13-8.

   
    If Pin 17, 18 or 19 is shorted to ground, GO to 13-10.
No
REPLACE diagnostic monitor. RECONNECT system. VERIFY system. REACTUATE system.

 

13-8 CHECK LH B-PILLAR SAFING SENSOR CIRCUIT

  • Disconnect LH B-pillar safing sensor connector.
  • Verify system.
  • Does air bag indicator flash a diagnostic trouble code 13?
Yes
LOCATE and SERVICE short to ground in wiring harness Circuit 614 (GY/O). GO to Diagnostic Trouble Code 51.

No
GO to 13-9.

 

13-9 VERIFY SHORT TO GROUND IN LH B-PILLAR SAFING SENSOR

  • Measure resistance from safing sensor connector Circuit 614 (GY/O) to ground.
  • Is resistance less than 10 ohms?




Yes
REPLACE LH B-pillar safing sensor. GO to Diagnostic Trouble Code 51.

No
LOCATE and SERVICE short to ground in wiring harness Circuit 623 (P/W). GO to Diagnostic Trouble Code 51.

 

13-10 CHECK SHORT TO GROUND IN CRASH SENSORS

  • If Pin 17 was shorted to ground, disconnect RH headlamp primary crash sensor. If Pin 18 was shorted to ground, disconnect center radiator primary crash sensor. If Pin 19 was shorted to ground, disconnect LH headlamp primary crash sensor.
  • Measure the resistance across the two circuits in the disconnected sensor connector.
  • Is the resistance less than 750 ohms?
Yes
REPLACE sensor. GO to Diagnostic Trouble Code 51.

No
LOCATE and SERVICE short to ground in wiring harness Circuits 617 (PK/O), 619 (PK/W) or 621 (W/Y). GO to Diagnostic Trouble Code 51.