1996 Bronco/F-Series

Section 18-01: Wiring and Circuit Protection

1996 F-150, F-250, F-350, F-Super Duty Chassis Cab, Motorhome Chassis, and Bronco Workshop Manual

DIAGNOSIS AND TESTING

Pinpoint Tests, Trailer Towing Package Wiring

PINPOINT TEST A: TRAILER TOWING PACKAGE WIRING

A1 CHECK LIGHTING OPERATION

Disconnect trailer from vehicle and disconnect trailer feed wiring from rear lamp wiring.
Check operation of vehicle exterior lighting systems for any concerns.

Does the exterior lighting system of vehicle operate properly?

Yes	No
GO to A2.	SERVICE any vehicle exterior lighting concerns. REFER to Section 17-01.

A2 CHECK FUSES

Check the following fuses:

Fuse Panel
Fuse No. 4
Power Distribution Box
Fuse No. 4, 5, 6, 7, 18, 21

Are fuses OK?

Yes	No
GO to A3.	SERVICE as required. RETEST trailer lighting system. If concern is still present, GO to A3.

A3 CHECK TRAILER GROUND FEED

Using a volt-ohmmeter, check resistance between Circuit 206 (W) of trailer feed wiring end and known good ground.

Is resistance less than 5 ohms?

Yes	No
GO to A4.	GO to A9.

A4 CHECK CIRCUIT 962 (BR/W) FOR BATTERY VOLTAGE

Key in run, turn the headlamps on.
Using a volt-ohmmeter, measure voltage of trailer feed wiring end Circuit 962 (BR/W).

Is voltage greater than 10V?

Yes	No
GO to A5.	GO to A9.

A5 CHECK TRAILER RH TURN, STOP AND HAZARD FEED

Key in run, turn the hazard lamps on.
Using a volt-ohmmeter, measure voltage of trailer feed wiring end Circuit 64 (DG).

Does voltage modulate from greater than 10V to less than 1V?

Yes	No
GO to A6.	GO to A15.

A6 CHECK TRAILER LH TURN, STOP AND HAZARD FEED

Key in run, turn the hazard lamps on.
Using a volt-ohmmeter, measure voltage of trailer feed wiring end Circuit 52 (Y).

Does voltage modulate from greater than 10V to less than 1V?

Yes	No
GO to A7.	GO to A15.

A7 CHECK TRAILER BATTERY FEED

Key in run.
Using a volt-ohmmeter, measure voltage of trailer feed wiring end Circuit 49 (O).

Is voltage greater than 10V?

Yes	No
GO to A8.	GO to A9.

A8 CHECK TRAILER ELECTRIC BRAKE FEED

Key in run.
With the assistance of another person, while pressing the brake pedal, measure voltage of trailer feed wiring end Circuit 43 (DB).

Is voltage greater than 10V?

Yes	No
The vehicle is operating properly. Have trailer serviced by an authorized camper/trailer repair center.	SERVICE open in Circuit 43 (DB) of trailer feed wiring or electronic brake control system. RETEST system.

A9 CHECK RELAY GROUND

Locate relay connector for circuit.
Using a volt-ohmmeter, check resistance of Pin 85 of trailer battery charge relay connector and known good ground.

Is resistance less than 5 ohms?

Yes	No
GO to A10.	SERVICE open in Circuit 57 (BK) of engine control sensor wiring. RETEST system.

A10 CHECK RELAY POWER

Locate relay connector for circuit.
Using a volt-ohmmeter, check voltage of Pin 86 of trailer battery charge relay connector.

Is voltage greater than 10V?

Yes	No
GO to A11.	SERVICE open in Circuit 298 (P/O) of engine control sensor wiring. RETEST system.

A11 CHECK TRAILER MARKER LAMPS RELAY FEED

Key in run, turn the headlamps on.
Using a volt-ohmmeter, measure voltage of Circuit 14 (BR) of the trailer running lamp relay connector.

Is voltage greater than 10V?

Yes	No
GO to A12.	SERVICE open in Circuit 14 (BR) of engine control sensor wiring. RETEST system.

A12 CHECK TRAILER MARKER LAMPS RELAY GROUND

Locate relay connector for circuit.
Using a volt-ohmmeter, check resistance of Circuit 57 (BK) of trailer marker lamps relay connector and known good ground.

Is resistance less than 5 ohms?

Yes	No
GO to A13.	SERVICE open in Circuit 57 (BK) of engine control sensor wiring. RETEST system.

A13 CHECK TRAILER BACKUP LAMPS RELAY GROUND

Locate relay connector for circuit.
Using a volt-ohmmeter, check resistance of Pin 85 of trailer backup lamps relay connector and known good ground.

Is resistance less than 5 ohms?

Yes	No
GO to A14.	SERVICE open in Circuit 57 (BK) of engine control sensor wiring. RETEST system.

A14 CHECK TRAILER BACKUP LAMP RELAY FEED

Locate relay connector for circuit.
Using a volt-ohmmeter, check voltage of Pin 30 of trailer backup lamps relay connector.

Is voltage greater than 10V?

Yes	No
GO to A15.	SERVICE open in Circuit 963 (BK/LG) of engine control sensor wiring. RETEST system.

A15 CHECK TRAILER RH TURN, STOP AND HAZARD FEED

Key in run, turn the hazard lamps on.
Using a volt-ohmmeter, measure voltage of Pins 6 and 3 of the trailer adapter connector.

Does voltage modulate from greater than 10V to less than 1V?

Yes	No
GO to A16.	SERVICE open in Circuit 52 or Circuit 9 for left side or Circuit 64 or Circuit 5 for right side. RETEST system.

A16 CHECK TRAILER WIRING FEED WIRING

Using a volt-ohmmeter, check the following relay pins and circuits for continuity:

Trailer battery charging relay Pin 4 to trailer feed wiring end Circuit 49 (O).
Trailer backup lamps relay Pin 30 to trailer feed wiring end Circuit 963 (BK/LG).
Trailer marker lamps relay Circuit 962 (BR/W) to trailer feed wiring end Circuit 962 (BR/W).

Do all circuits have continuity?

Yes	No
REPLACE relay for circuit not functioning properly. RETEST system.	SERVICE open in trailer feed wiring for circuit(s) that indicated no continuity. RETEST system.