What fuse powers the 1994 Bronco 4WABS system?

A 30A fuse in position H of the engine compartment fuse box (hot at all times), feeding circuit 532 O/Y. The fuse box layout is on page 13-6.

What wire colors connect the 4WABS hydraulic unit valves to the control module?

Through connector C121: 495 T (left front iso), 496 O (left front dump), 497 W (right front iso), 498 PK (right front dump), 499 GY/BK (rear iso), and 510 T/R (rear dump).

What does 4WABS Relay #2 do?

When energized, it directs 12V voltage to the 4WABS pump motor. It receives power on circuit 534 Y/LG, and its coil is controlled by the module on circuit 533 T/R via C119.

What does the 4WABS pump motor do when energized?

It pumps high pressure fluid into the master cylinder, causing the brake pedal to be forced up. Its speed sensor also provides feedback (wires 462 P and 604 O/R) to the 4WABS control module.

How does the speed signal reach the 4WABS control module?

The programmable speedometer/odometer module receives input from the rear axle sensor, converts it to a standard 8,000 pulses per mile signal, and provides it to the module (pin 39, vehicle speed input via circuits 491 O/LB and 530 LG/Y), the PCM, and the speed control servo/amplifier assembly.

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1994 Ford Bronco 4WABS ABS Wiring Diagram - EVTM Page 42-4

1994 Ford Bronco F-Series 4WABS anti-lock brake wiring diagram page 42-4

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1994 Bronco/F-Series rear anti-lock brake (4WABS) schematic: hydraulic control valve solenoids, dump valves, wheel-speed sensors, pump motor relay, 4WABS control module and PSOM speedometer module.

AI caption February 2020 · Photo 2996 of 3001

This is page 42-4 of the 1994 Ford Bronco/F-Series Electrical and Vacuum Troubleshooting Manual (EVTM), showing the Bronco 4-Wheel Anti-lock Brake System (4WABS) wiring diagram. It details the 4WABS hydraulic unit containing three sets of solenoid iso/dump valves (left front, right front, rear) with connector C121 pinouts and wire circuits 495 T, 496 O, 497 W, 498 PK, 499 GY/BK, and 510 T/R feeding the 4WABS control module (grid 151-4 E9). Power comes from a 30A fuse (position H) in the engine compartment fuse box on circuit 532 O/Y, which also links to the trailer relay box (pages 42-3 and 42-5). 4WABS Relay #2, when energized, directs voltage (circuit 534 Y/LG in, 539 PK/LB and 533 T/R control) to the 4WABS pump motor, which pumps high-pressure fluid into the master cylinder; the pump motor speed sensor (circuits 462 P and 604 O/R) provides feedback to the control module. The programmable speedometer/odometer module provides an 8,000 pulses-per-mile vehicle speed signal (circuits 491 O/LB, 530 LG/Y) to the module, PCM, and speed control servo. Grounds are at G100 and G101 via wire 57 BK. Cross-references include fuse box page 13-6 and instrument cluster page 60-7.

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Frequently asked questions

What fuse powers the 1994 Bronco 4WABS system?: A 30A fuse in position H of the engine compartment fuse box (hot at all times), feeding circuit 532 O/Y. The fuse box layout is on page 13-6.
What wire colors connect the 4WABS hydraulic unit valves to the control module?: Through connector C121: 495 T (left front iso), 496 O (left front dump), 497 W (right front iso), 498 PK (right front dump), 499 GY/BK (rear iso), and 510 T/R (rear dump).
What does 4WABS Relay #2 do?: When energized, it directs 12V voltage to the 4WABS pump motor. It receives power on circuit 534 Y/LG, and its coil is controlled by the module on circuit 533 T/R via C119.
What does the 4WABS pump motor do when energized?: It pumps high pressure fluid into the master cylinder, causing the brake pedal to be forced up. Its speed sensor also provides feedback (wires 462 P and 604 O/R) to the 4WABS control module.
How does the speed signal reach the 4WABS control module?: The programmable speedometer/odometer module receives input from the rear axle sensor, converts it to a standard 8,000 pulses per mile signal, and provides it to the module (pin 39, vehicle speed input via circuits 491 O/LB and 530 LG/Y), the PCM, and the speed control servo/amplifier assembly.