Ford RABS Rear Antilock Brake System Troubleshooting Chart (1992 Bronco)
Reference · 1992-1996 BroncoAll 143 service procedures
Ford RABS rear antilock brake troubleshooting flowchart. Branches by yellow/red bulb behavior to Tests A-G checking module harness, 15A/20A warning fuses, fluid level sensor, and wheel lock-up.
Part of 1992-1996 Ford Bronco Service Procedures
This document is a Rear Antilock Brake System (RABS) troubleshooting flowchart, drawing number CH6257-D. It guides a technician through diagnosing RABS warning light behavior, starting with obtaining a flashout code if the RABS light is on while the vehicle is running, then cycling the ignition from OFF to RUN and observing the 2-second "REAR ANTILOCK" bulb test. Depending on whether the yellow RABS bulb and red BRAKE bulb light, the chart directs the user to specific diagnostic tests: Test A (module harness connector, module ground, antilock light power, 15 amp warning fuse, bulb and wiring), Test G (master cylinder connector, red brake warning light, fluid level sensor/wiring), Test E (intermittent module power, grounded diagnostic lead, module ground), Test C (low brake fluid, master cylinder float, diode/resistor element, antilock valve switch), Test B (parking brake and switch, diesel low vacuum switch), Test F (vehicle stop light circuit), Test D/D2 (flashout code retrieval, RABS 20 amp fuse, wiring shorts), and Test F3 (excitor ring, sensor output/gap, rear brake mechanical problems, computer module). It concludes with a road test at 10 mph to check for rear wheel lock-up; if rear wheels don't lock, the system is functioning and intermittent problems should be checked via flashout code 6.
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Frequently asked questions
- What should I do first if the RABS light is on while the vehicle is running?
- Obtain the flashout code before shutting the engine off, then turn the ignition switch from OFF to RUN and observe the 2-second "REAR ANTILOCK" bulb test.
- What does the chart say to check if the yellow RABS bulb does not light?
- Go to Test A to check the module harness connector, module ground, antilock light power, the 15 amp warning fuse, power to the 15 amp warning fuse, and the antilock bulb and wiring.
- What is checked if there is no flashout code?
- Test D2: master cylinder harness connector, RABS 20 amp fuse, shorts in module harness connector wiring, power to module, voltage at fluid level sensor, and grounded diagnostic lead.
- What happens if the rear wheels lock during the road test?
- Continue with Test F3 to check wiring from module to brake switch, excitor ring, sensor output, sensor gap, mechanical problems in rear brakes, and the computer module.
- What if the rear wheels don't lock during the road test?
- The system is functioning OK; consider a possible intermittent wiring problem or a problem that only shows up during driving, and refer to flashout code 6 for possible areas of concern.
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