Tone rings — also called reluctor rings or encoder rings — provide the toothed or magnetic pattern that wheel speed sensors read to calculate wheel rotation. When a tone ring cracks, corrodes, wobbles, or loses teeth, it generates erratic or missing pulses that are indistinguishable from a failed sensor. These faults cause intermittent ABS, traction […]
If your scan tool reports “no response,” “lost communication,” or a U0121 (lost communication with ABS control module), don’t assume the module has failed. The vast majority of ABS communication faults trace back to a blown fuse, bad ground, corroded connector, or a CAN bus fault — not a dead module. The ABS hydraulic unit […]
When a vehicle comes in with multiple U-codes, modules dropping offline, or a scan tool that cannot communicate with half the network, the termination resistance test should be one of the first things you do. It takes thirty seconds, requires only a multimeter, and tells you immediately whether the physical CAN bus has a major […]
Wheel speed sensor codes are among the most commonly misdiagnosed ABS faults — not because the diagnosis is technically difficult, but because the wrong test is applied first. Resistance testing a modern active sensor tells you almost nothing useful. Replacing the sensor before inspecting the tone ring means fitting a new part into the same […]