Ford Mustang (1999-2004) Service Manual: Stoplamps

Refer to Wiring Diagrams Cell 90 , Turn/Stop/Hazard Lamps for schematic and connector information.

Special Tool(s)

73III Automotive Meter or equivalent 105-R0057

Inspection and Verification

1. Verify the customer concerns.

2. Visually inspect for the following obvious signs of mechanical or electrical damage.

Visual Inspection Chart

Mechanical

Electrical

  • Brake pedal position (BPP) switch
  • Central junction box (CJB) fuse 41 (15A)
  • Circuitry
  • Bulb(s)

3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

4. If the concern is not visually evident, determine the symptom and refer to the Symptom Chart.

Symptom Chart

Condition Possible Sources Action
  • The stoplamps are inoperative
  • Central junction box (CJB) fuse 41 (15A).
  • Circuitry.
  • Brake pedal position (BPP) switch
  • Go To Pinpoint Test G .
  • One or more stoplamps are inoperative
  • Circuitry.
  • Multifunction switch
  • Go To Pinpoint Test H
  • The stoplamps are on continuously
  • Brake pedal position (BPP) switch.
  • Multifunction switch
  • Go To Pinpoint Test I .

Pinpoint Tests

PINPOINT TEST G: THE STOPLAMPS ARE INOPERATIVE

Test Step Result / Action to Take
G1 CHECK CIRCUIT 10 (LG/RD) FOR AN OPEN Yes

GO to G2 .

No

REPAIR the circuit. TEST the system for normal operation
  • Disconnect: Brake Pedal Position (BPP) Switch C278.
  • Measure the voltage between the BPP switch C278, circuit 10 (LG/RD), harness side and ground.

  • Is the voltage greater than 10 volts?
G2 CHECK THE CIRCUIT 810 (RD/LG) FOR AN OPEN Yes

INSTALL a new BPP switch.

REFER to Lamp Switch- Brake Pedal Position (BPP) in this section. TEST the system for normal operation.

No

REPAIR circuit 810 (RD/LG) or 569 (DG) as necessary.

TEST the system for normal operation.
  • Connect a 10A fused jumper wire between C278, circuit 10 (LG/RD), harness side and C278, circuit 810 (RD/LG), harness side.

  • Do the stoplamps illuminate?

PINPOINT TEST H: ONE OR MORE STOPLAMPS ARE INOPERATIVE

Test Step Result / Action to Take
H1 CHECK THE VOLTAGE TO THE INOPERATIVE STOPLAMP Yes

REPAIR circuit 1205 (BK). TEST the system for normal operation.

No

If high mounted stoplamp, REPAIR circuit 569 (DG). TEST the system for normal operation.

If rear stoplamp, GO to H2 .
  • Disconnect: Inoperative Stoplamp.
  • If a rear stoplamp is inoperative, measure the voltage between the inoperative stoplamp connector circuit 9 (LG/OG) (LH) or circuit 5 (OG/LB) (RH), harness side and ground, while pressing the brake pedal.

  • If the high mounted stoplamp is inoperative, measure the voltage between the inoperative high mounted stoplamp C475 (C4199 for Cobra) pin 1, circuit 569 (DG), harness side and ground while pressing the brake pedal.

  • Is the voltage greater than 10 volts?
H2 CHECK CIRCUIT 9 (LG/OG) OR 5 (OG/LB) FOR AN OPEN Yes

INSTALL a new multifunction switch.

REFER to Section . TEST the system for normal operation.

No

REPAIR the circuit in question. TEST the system for normal operation.
  • Disconnect: Multifunction Switch C202b.
  • Measure the resistance between the inoperative stoplamp connector and multifunction switch C202b pin 9, circuit 9 (LG/OG) (LH), or C202b pin 5, circuit 5 (OG/LB) (RH).

  • Is the resistance less than 5 ohms?

PINPOINT TEST I: THE STOPLAMPS ARE ON CONTINUOUSLY

Test Step Result / Action to Take
I1 CHECK THE BRAKE PEDAL POSITION (BPP) SWITCH Yes

GO to I2 .

No

INSTALL a new BPP switch. REFER to Lamp Switch- Brake Pedal Position (BPP) . TEST the system for normal operation.
  • Key in OFF position.
  • Disconnect: BPP Switch C278.
  • Do the stoplamps continue to illuminate?
I2 CHECK THE SPEED CONTROL SYSTEM Yes

GO to I3 .

No

REFER to Section.
  • Disconnect: Speed Control Servo C122.
  • Do the stoplamps continue to illuminate?
I3 CHECK CIRCUIT 511 (LG) FOR SHORT TO POWER Yes

GO to I4 .

No

REPAIR the circuit. TEST the system for normal operation
  • Disconnect: Central Junction Box (CJB) Fuse 35 (15A).
  • Do the stoplamps continue to illuminate?
I4 CHECK CIRCUIT 810 (LG/RD) FOR SHORT TO POWER Yes

GO to I5 .

No

REPAIR the circuit. TEST the system for normal operation
  • Disconnect: CJB Fuse 41 (15A).
  • Do the stoplamps continue to illuminate?
I5 CHECK THE MULTIFUNCTION SWITCH Yes

If the high mounted stoplamp is illuminated, REPAIR circuit 569 (DG) or 511 (LG) as necessary. TEST the system for normal operation.

If only the LH stoplamp is illuminated, REPAIR circuit 9 (LG/OG). TEST the system for normal operation.

If only the RH stoplamp is illuminated, REPAIR circuit 5 (OG/LB). TEST the system for normal operation.

No

INSTALL a new multifunction switch. REFER to Section. TEST the system for normal operation
  • Disconnect: Multifunction Switch C202b.
  • Do the stoplamps continue to illuminate?
    Headlamps
    Refer to Wiring Diagrams Cell 85 , Headlamps for schematic and connector information. Special Tool(s) 73III Automotive Meter or equivalent 105-R0057 Inspection and Verification ...

    Turn Signal and Hazard Lamps
    Refer to Wiring Diagrams Cell 90 , Turn/Stop/Hazard Lamps for schematic and connector information. Special Tool(s) 73 III Automotive Meter 105-R0057 or equivalent Inspection and Ver ...

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