A tractor manufactured on or after March 1, 2001 is towing a trailer manufactured after March 1, 1998, which is required to have its own ABS. If that trailer's ABS develops a malfunction, where does federal regulation require the driver to see a warning?

Explanation

Federal regulation requires certain truck tractors to be wired so a trailer's ABS malfunction shows up on a trailer ABS malfunction lamp inside the cab of the towing vehicle, not just on the trailer itself. 49 CFR 393.55(d)(2) requires truck tractors manufactured on or after March 1, 2001, and other single-unit vehicles equipped to tow an air-braked vehicle, to have an electrical circuit capable of transmitting a malfunction signal from the towed vehicle's ABS to that in-cab lamp, so the driver does not have to inspect the trailer directly to know something is wrong. Saying the driver can only see a warning on the trailer's exterior is wrong because that separate exterior lamp, required by 393.55(e), exists alongside the in-cab lamp, not instead of it. The fuel gauge is wrong because ABS malfunction warnings use their own dedicated indicator, never a repurposed, unrelated gauge. Saying there is no requirement is wrong because the wiring and in-cab lamp are exactly what paragraph (d)(2) mandates for a properly equipped combination.

Source: 49 CFR 393.55(d)(2)