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DTC codes / C00xx · Brakes, steering and suspension / C0038

C0038Right Rear Wheel Speed Sensor Circuit Range/Performance

C0038 means the anti-lock brake system (ABS) module has detected an abnormal signal from the right rear wheel speed sensor circuit, typically an erratic or out-of-range voltage pattern during driving. The computer compares that signal against expected wheel speed and flags the circuit as performing outside its valid range.

SystemChassis
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaBrakes, steering and suspension

Symptoms you may notice

  • ABS warning light illuminated on the dashboard
  • Traction control or stability control warning light also on
  • ABS disabled during braking, with possible wheel lockup in a panic stop
  • Speedometer fluctuation or inaccuracy on some vehicles
  • Often no symptoms besides the warning light

Common causes, most likely first

  1. Damaged or corroded wheel speed sensor connector or wiring at the right rear wheel
  2. Debris, metal shavings, or rust buildup on the sensor tip or tone ring
  3. Failed right rear wheel speed sensor
  4. Cracked or missing tone ring (reluctor ring) on the right rear hub or axle
  5. Excessive wheel bearing play or hub runout disturbing the sensor air gap
  6. Chafed or broken wire in the harness between the sensor and ABS module
  7. Internal ABS module fault on the right rear sensor input channel

How to diagnose and fix it

  1. Inspect the right rear sensor, connector, and wiring for corrosion, damage, or debris and clean or repair as needed
  2. Remove the sensor and check the tone ring for cracks, missing teeth, or heavy rust contamination
  3. Measure sensor resistance and compare to the manufacturer's specification, then check for an AC voltage signal while spinning the wheel
  4. Check the sensor air gap and wheel bearing play at the right rear hub, correcting any excessive runout
  5. Back-probe the sensor circuit at the ABS module connector and perform a wiggle test on the harness to find intermittent opens or shorts
  6. If the sensor and wiring test good, verify the ABS module is receiving and processing the signal correctly before condemning the module

Why the right rear sensor keeps failing

  • A common miss is a tone ring that looks intact but has a fine crack or rust jacking that disturbs the signal only at certain speeds, so a static resistance test passes.
  • Rear wheel bearings on many vehicles are part of the hub assembly, and early bearing noise or play can set C0038 long before the driver hears anything.
  • Aftermarket brake work or suspension repairs can leave the sensor harness routed too close to a moving component, causing an intermittent short that mimics a failed sensor.
  • The code does not always mean the sensor itself is bad; a poor ground or voltage supply shared with other chassis sensors can corrupt the signal.
  • On some vehicles, the ABS module logs C0038 when the battery voltage is low during cranking, so clear the code and verify charging system health before replacing parts.

Can I keep driving with C0038?

You can usually drive the vehicle, but the ABS and traction control systems are disabled, so braking distances may increase on slippery surfaces. Avoid hard braking or emergency maneuvers until the fault is repaired, and have it diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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