Wheel Speed Sensor Woes
This bulletin applies to 2007-2017 GMC Acadia vehicles. In some cases, the ABS Service Traction Control System, and/or Service StabiliTrak telltale lights may be on. During initial scan for EBCM module diagnostic codes, you may find one or more of the following DTCs: C0035-C0050 with specific symptom bytes 18, 5A or 0F.
For vehicles equipped with electric power steering, the operator may also notice a Service Steering message displayed and will experience a heavier steering feel at low speed or static maneuvers. This will be accompanied with the power steering control module setting DTC U0415. This is a normal default action with the loss of a wheel speed sensor signal.
A brief and intermittent noise, click ratchet, grind or ABS pump motor noise may be heard inside the vehicle at parking lot speeds. A flashing Traction Control or StabilitTrak telltale may be displayed at low speeds.
These conditions may be caused by single or multiple pieces of ferrous metallic debris stuck to the wheel speed sensor magnetic encoder ring. Inspect and clean the encoder ring. Note that this information is not applicable to capped wheel bearings.
Some new model vehicles today have begun to use a different type of wheel speed sensor encoder ring or tone wheel. Instead of a traditional mechanical type tooth tone wheel, the wheel speed sensor tone wheel is now made of a magnetized nitrile rubber ring, typically brown in color.
This magnetic encoder consists of multiple North and South pole pairs surrounding the outer circumference. When this magnetic encoder ring rotates and passes by the wheel speed sensor head, it generates a sine wave in the wheel speed sensor. The wheel speed sensor converts an analog signal to a digital square wave, and typical digital signal values switch between 7mA (low) and 14 mA (high) DC current.