C0041

C0041 is a generic chassis code for a fault in the left rear wheel speed sensor circuit — the EBCM/ABS module is not seeing the signal it expects from the LR WSS during a wheel-rotation event, either because the sensor is open/shorted, the air gap is wrong, the tone ring is damaged, or the harness has broken between the sensor and the module. Cheapest-first ladder on a shop floor: (1) Scan live data for all four wheel-speed sensors with the vehicle on a lift, spin the LR wheel by hand at ~1 rev/sec, and watch the signal. Passive (variable-reluctance) sensors should put out 0.4-1.5V AC at slow rotation, climbing with speed; active (Hall-effect) sensors output a 0.2-1V DC square wave (or a digital frame on newer GM platforms) with amplitude essentially fixed and frequency climbing with speed — flat 0V or pinned battery voltage means circuit fault before sensor fault. (2) Resistance-check a passive WSS at the connector with a DMM: most spec 1,000-2,500 ohms; open circuit or below 200 ohms is a dead sensor. Active sensors don't ohm-check — back-probe the signal wire with the connector seated, key-on, and look for the reference voltage (typically 12V supply, 5V signal idle). (3) Inspect the harness routing along the trailing arm or behind the rear knuckle — rodent chew and rub-through at the body grommet are the two most common harness failures on this circuit. (4) Pull the sensor and measure air gap to the tone ring with a feeler gauge (spec is usually 0.020-0.050 inches; if you can't measure it because the ring is missing, that IS the diagnosis). Expensive-misdiagnosis caveat: GM trucks 1999-2007 — the ABS tone ring is pressed onto the CV axle or rear hub and rusts off completely, leaving a clean stub of axle and an air gap that reads infinite. The WSS itself is fine, but replacing the sensor doesn't fix the missing tone ring — you replace the axle, hub, or tone ring (some are available as a stamped-steel slip-on repair part) and the code clears.

Vehicle-specific patterns: 1999-2007 GM trucks (Silverado/Sierra/Tahoe/Yukon/Suburban) with the Kelsey-Hayes 325 EBCM throw C0041 from the trifecta of rusted-off tone rings on the rear axle shafts, corroded sensor connectors at the rear-axle harness junction, and water ingress into the EBCM itself — diagnose tone ring first (visual inspection through the brake-drum or rotor backing plate) before condemning anything else. 1997-2014 Ford F-150 with rear hub-mounted WSS as an integrated assembly throws C0041 when the wheel-bearing/hub assembly fails — the bearing roughness destroys the magnetic encoder ring inside the hub, so the fix is a $180-$300 hub assembly rather than a separate sensor (you cannot buy the sensor alone on these). 2008-2014 Dodge Grand Caravan/Chrysler Town & Country throws C0041 from rear toe-link sensor harness rub-through where the WSS pigtail clips to the trailing arm — the rear suspension articulates enough to wear through the loom. 2003-2009 Toyota 4Runner/GX470 throws C0041 from corroded sensor mounting bolts that seize the WSS into the rear knuckle; the sensor body breaks off during removal and the bore needs to be drilled and re-tapped. Estimated repair: $80 to $450.