Part 4 — The Repair and Final Lesson The front R-12 style relay valve had been replaced before, but the connected ABS modulators were not replaced at that time because the shop did not have the full kit. Later, I replaced the sensors and the steer axle ABS modulator/connected parts that go together. After the full repair, the problem disappeared. Day 3 driving after the repair: no lights, no radar fault, no annoying beeping, and the braking stayed smooth. My takeaway: A truck can show Adaptive Cruise Fault / Radar Fault, but the real cause may be the ABS or brake air system. In my case, the chain looked like this: Air dryer heater problem → water in air tanks → ABS sensors/modulators affected → ABS fault 802 → adaptive cruise/radar disabled → cruise disabled and dash beeping → sensors and steer ABS modulator parts repaired → problem gone Do not replace the radar first just because the dash says radar. Check the ABS codes, air dryer, moisture in the tanks, wiring, grounds, wheel speed sensors, and ABS modulators. Sometimes the warning on the dash is only the symptom — not the root cause.