Section 13-09: Gauges, Warning Devices, Miscellaneous—Electronic
1993 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Gauges, Warning Devices, Miscellaneous—Electronic

Check system fuse before proceeding.



Electronic Warning Chime Wiring Diagram








NOTE: The following step-by-step diagnosis must be performed to obtain reliable results. If a specific failure condition is known, refer to the Electrical and Vacuum Troubleshooting Manual to quickly determine root cause and corrective action.



ELECTRONIC WARNING CHIME DIAGNOSIS
Terminal No. Circuit Wire Color Function
1 450 DG/LG Warning chime module to safety belt warning indicator
2 640 R/Y Ignition (RUN or START) to warning chime module
4 159 R/PK Door jamb switch to warning chime module
5 14 BR Headlamp switch to warning chime module
6 158 BK/PK Key warning switch to warning chime module
9 85 BR/LB Safety belt switch to warning chime module
10 57 BK Ground to warning chime module

 

PINPOINT TEST A: ELECTRONIC WARNING CHIME DIAGNOSIS

 

A1 CHECK WARNING CHIME SYSTEM FUSE

Yes
GO to A2.

No
REPLACE fuse.

 

A2 CHECK FOR VOLTAGE AT CIRCUIT 640 (R/Y)

Yes
GO to A3.

No
CHECK Circuit 640 (R/Y) back to ignition switch. SERVICE as required. REPEAT A2.

 

A3 CHECK FOR GROUND AT CIRCUIT 57 (BK)

  • Connect a 12-volt test lamp between Circuit 640 (R/Y) and 57 (BK) in warning chime connector.
  • Turn ignition switch to RUN.
  • Does test lamp light?
Yes
GO to A4.

No
CHECK Circuit 57 (BK) back to body ground. SERVICE as required. REPEAT A3.

 

A4 CHECK CKT 450 (DG/LG) AND SAFETY BELT WARNING LAMP BULB

  • Connect jumper between Circuit 450 (DG/LG) and Circuit 640 (R/Y) in warning chime module connector.
  • Turn ignition switch to RUN.
  • Does safety belt warning indicator light?
Yes
GO to A5.

No
CHECK circuit 450 (DG/LG) back to safety belt warning indicator bulb. CHECK bulb. SERVICE as required. REPEAT A4.

 

A5 CHECK FOR GROUND AT CIRCUIT 85 (BR/LB)

  • Unbuckle driver side safety belt.
  • Connect a 12-volt test lamp between Circuit 85 (BR/LB) and Circuit 640 (R/Y) in warning chime connector.
  • Turn ignition switch to RUN.
  • Does test lamp light?
Yes
GO to A6.

No
CHECK Circuit 85 (BR/LB) back to safety belt switch. SERVICE as required. REPEAT A5.

 

A6 CHECK FOR GROUND AT CIRCUIT 158 (BK/PK)

  • Insert key in ignition.
  • Connect a 12-volt test lamp between Circuit 158 (BK/PK) and Circuit 640 (R/Y) in warning chime connector.
  • Turn ignition switch to RUN.
  • Does test lamp light?
Yes
GO to A7.

No
CHECK Circuit 158 (BK/PK) back to ignition key cylinder switch. SERVICE as required. REPEAT A6.

 

A7 CHECK FOR VOLTAGE AT CIRCUIT 159 (R/PK)

  • Connect a 12-volt test lamp between Circuit 159 (R/PK) in warning chime connector and a known good ground.
  • Open driver's door.
  • Does test lamp light?
Yes
GO to A8.

No
CHECK Circuit 159 (R/PK) back to courtesy lamp switch. SERVICE as required. REPEAT A7.

 

A8 CHECK FOR VOLTAGE AT CIRCUIT 14 (BR)

  • Connect a 12-volt test lamp between Circuit 14 and a known ground.
  • Pull headlamp switch ON.
  • Does test lamp light?
Yes
GO to A9.

No
CHECK Circuit 14 back to headlamp switch. SERVICE as required. REPEAT A8.

 

A9 CHECK WARNING CHIME MODULE OPERATION

  • Connect warning chime module.
  • Check for proper operation of: Safety belt warning. Key-in-ignition warning. Headlamp switch on warning. Tripminder audible tone.
All warnings operate properly
System operating properly.

One, two, or three warnings inoperative
CHECK back through appropriate circuit(s). SERVICE as necessary. REPEAT A9.

All warnings not operating
REPLACE warning chime module. REPEAT A9.