Ford Mustang (1999-2004) Service Manual: Reversing Lamps

Refer to Wiring Diagrams Cell 93 , Backup Lamps for schematic and connector information.

Special Tool(s)

73III Automotive Meter or equivalent 105-R0057

Inspection and Verification

1. Verify the customer concern by operating the reversing lamps.

2. Visually inspect for obvious signs of mechanical and electrical damage; refer to the following chart:

Visual Inspection Chart

Mechanical Electrical
  • Damaged digital transmission range (DTR) sensor (automatic transmission [A/T])
  • Damaged reversing lamp switch (manual transmission [M/T])
  • Blown central junction box (CJB) Fuse 11 (15A)
  • Damaged wiring harness
  • Loose or corroded connections
  • Damaged reversing lamp
  • Damaged DTR sensor (automatic transmission [A/T])
  • Damaged reversing lamp switch (manual transmission [M/T])

3. If the concern is not visually evident, determine the symptom and proceed to Symptom Chart.

Symptom Chart

Condition Possible Sources Action
  • The reversing lamps are inoperative
  • CJB Fuse 11 (15A).
  • Bulbs.
  • Circuitry.
  • DTR sensor (A/T).
  • Reversing lamp switch (M/T).
  • GO to Pinpoint Test R .
  • The individual reversing lamp is inoperative
  • Bulb.
  • Circuitry.
  • GO to Pinpoint Test S .
  • The reversing lamps are on continuously
  • Circuitry.
  • DTR sensor (A/T).
  • Reversing lamp switch (M/T)
  • GO to Pinpoint Test T

Pinpoint Tests

PINPOINT TEST R: THE REVERSING LAMPS ARE INOPERATIVE

Test Step Result / Action to Take
R1 CHECK THE VOLTAGE TO THE DTR SENSOR (A/T) OR THE REVERSING LAMP SWITCH (M/T) Yes

GO to R2 .

No

REPAIR the circuit. TEST the system for normal operation.
  • Key in OFF position.
  • Disconnect: DTR Sensor C167 (A/T).
  • Disconnect: Reversing Lamp Switch C169 (M/T).
  • Key in ON position.
  • If equipped with A/T, measure the voltage between DTR sensor C167 Pin 9, Circuit 1087 (OG), harness side and ground.

  • If equipped with M/T, measure the voltage between reversing lamp switch C169, Circuit 1087 (OG), harness side and ground.

  • Is the voltage greater than 10 volts?
R2 CHECK CIRCUIT 140 (BK/PK) FOR OPEN Yes

INSTALL a new DTR sensor (A/T) or reversing lamp switch (M/T);  TEST the system for normal operation.

No

GO to R3 .
  • Key in OFF position.
  • If equipped with A/T, measure the resistance between DTR sensor C167 Pin 11, Circuit 140 (BK/PK), harness side and ground.

  • If equipped with M/T, measure the resistance between reversing lamp switch C169, Circuit 140 (BK/PK), harness side and ground.

  • Is the resistance less than 5 ohms?
R3 CHECK REVERSING LAMPS GROUND Yes

REPAIR Circuit 140 (BK/PK) for open. TEST the system for normal operation.

No

REPAIR the circuit. TEST the system for normal operation
  • Disconnect: Inoperative Reversing Lamp.
  • Measure the resistance between LH reversing lamp C451, Circuit 1205 (BK), or RH reversing lamp C461, Circuit 1205 (BK), harness side and ground.

  • Is the resistance less than 5 ohms?

PINPOINT TEST S: THE INDIVIDUAL REVERSING LAMP IS INOPERATIVE

Test Step Result / Action to Take
S1 CHECK REVERSING LAMPS GROUND Yes

REPAIR Circuit 140 (BK/PK) for open.

TEST the system for normal operation.

No

REPAIR the circuit.

TEST the system for normal operation.
  • Key in OFF position.
  • Disconnect: Inoperative Reversing Lamp.
  • Measure the resistance between LH reversing lamp C451, Circuit 1205 (BK), or RH reversing lamp C461, Circuit 1205 (BK), harness side and ground.

  • Is the resistance less than 5 ohms?

PINPOINT TEST T: THE REVERSING LAMPS ARE ON CONTINUOUSLY

Test Step Result / Action to Take
T1 CHECK THE CONTINUITY OF THE DTR SENSOR (A/T) OR THE REVERSING LAMP SWITCH (M/T) Yes

REPAIR Circuit 140 (BK/PK) for short to battery.

TEST the system for normal operation.

No

INSTALL a new DTR sensor (A/T) or reversing lamp switch (M/T); TEST the system for normal operation.
  • Key in OFF position.
  • Disconnect: DTR Sensor C167 (A/T).
  • Disconnect: Reversing Lamp Switch C169 (M/T).
  • Set the parking brake.
  • Key in ON position.
  • Select REVERSE.
  • Are the reversing lamps illuminated?
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