These are the parts that turn a brake warning light into a diagnostic session.
A wheel speed sensor can fail from debris, from a cracked tone ring or from a broken wire inside the harness. The code often points at a wheel where the real fault is a corroded connector half a metre away, so inspect the harness before ordering a sensor.
Modules are matched to the vehicle's configuration. Two modules with the same connector can carry different software for different axle ratios or brake packages, and a mismatch produces a permanent fault. Listings state the part number and, where the supplier provides it, the vehicles the module was programmed for.
Replacing a module on most vehicles requires programming, which is a dealer or independent-shop operation rather than a plug-and-play swap.
