C0245

C0245 means the ABS module is seeing a wheel speed sensor frequency error — the WSS signal is present but out of expected range relative to vehicle speed or the other three sensors. On a passive Hall-effect WSS (older GM/Ford), output is an AC sine wave that should produce 0.4-1.5V AC peak-to-peak at 30 mph rolling; on a modern active WSS (most 2005+ vehicles), output is a square-wave digital signal swinging 0.2-1.0V DC at idle and rising in frequency with wheel speed. Diagnostic order: (1) Inspect the tone ring at each wheel — bent, rusted, or missing teeth on the ring will produce a frequency error even with a perfect sensor; common on bearing replacements where the new hub's tone ring is missing a tooth or two from shipping damage. (2) Check the air gap at the sensor (0.5-1.5 mm typical) — too far means weak signal, too close means physical contact damage. (3) Back-probe the WSS connector with a DMM in AC volts (passive) or scope it (active) while spinning the wheel by hand — passive should produce visible AC voltage; active should show a clean square wave. (4) Check sensor resistance on passive sensors — typical 800-2,500 ohms; infinite means open coil, near-zero means shorted. Misdiagnosis caveat: rust buildup between the tone ring and the bearing race ('crusty wheel-speed-sensor disease') displaces the ring outward into the sensor or causes uneven gap — wire-wheel the rust off the bearing flange and reseat the ring before condemning a $80-$200 sensor.

Vehicle-specific patterns: 2004-2012 GM trucks (Silverado, Sierra, Tahoe) and Cadillac Escalade throw C0245 from rust packing into the front hub bearing assembly between the tone ring and the WSS; the fix is a complete hub replacement ($150-$400 per side) since the tone ring is integral to the hub. 2007-2014 Ford Edge/Flex/Explorer with the Haldex AWD system commonly throws C0245 from rear-wheel WSS harness chafe at the trailing arm. 2003-2009 Toyota 4Runner/Tacoma throws C0245 from corroded WSS connectors at the front uprights (salt-belt vehicles). 2002-2008 Mini Cooper R50/R53 throws C0245 from ABS ring damage during CV-axle replacement where techs pry against the ring teeth. Estimated repair: $80 (WSS replacement DIY) to $500 (complete hub assembly with bearing).