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I think I busted mine last night. Got the Hill decent fault with the ABS light on. Wasn't even driving too hard on it.
I seriously doubt you did... what happened to J was something of a "freak accident" IMHO... I've driven many, many miles on similar and worse trails without breaking a sensor as I'm sure many others have. Plus, if you break a sensor, you go into "full limp" mode and you'd know it.
I'd check your third brake light (above the rear window on the back of the cab) for signs that water got inside... and/or check your brake lights in general. My theory about the "hill descent fault" error is that it's often caused by a problem in the brake lamp circuit.