ABS light on your Ford Super Duty? It might not be the module

If your Ford Super Duty (F-250/350/450/550) has the ABS light on along with strange electrical symptoms, don't rush to quote the ABS module — a good share of these cases are actually water in the Battery Junction Box (BJB), not the module itself.

The codes that give away the pattern

C0020 and U3003 are the codes most associated with this Ford-documented TSB case. When they show up alongside other electrical symptoms — the engine that won't shut off, the horn sounding on its own, a no-start, a dead battery — the BJB is the first suspect.

Why replacing the ABS without checking the BJB fixes nothing

If water got into the BJB and the ABS module is healthy, swapping the whole ABS unit doesn't touch the real problem — you'll keep seeing the same symptoms after the replacement, except now you've also spent money on a part you didn't need.

Our process

We check the BJB for water intrusion first, before quoting any module. We cover the Ford Super Duty 2014-2022. Every replacement module, when one really is needed, requires mandatory VIN programming (PMI).