ABS and brakes

C0033 — Right Front Wheel Speed Sensor Circuit Malfunction

Severity: medium Drive with care, to a shop

What C0033 means

The ABS module monitors the signal from the right front wheel speed sensor and compares it with the other wheels. The sensor reads a toothed tone (exciter) ring that turns with the hub or axle. If the signal is missing, erratic or implausible, the module sets C0033 and disables the functions that depend on wheel speed data.

Symptoms

  • ABS warning light on
  • Traction and stability control disabled, with their lights on
  • ABS activating falsely at low speed
  • Erratic or dead speedometer on some models
  • Unexpected pulsing in the brake pedal

Possible causes

  1. Failed right front wheel speed sensor
  2. Damaged, cracked or dirty tone ring
  3. Broken, chafed or shorted wiring in the wheel well
  4. Corroded or loose sensor connector
  5. Metal debris stuck to the sensor tip
  6. Wrong sensor air gap after hub or brake work

How to diagnose

  1. Scan the ABS module and watch live wheel speed data for all four wheels while driving
  2. Inspect the sensor, its mounting and the harness for damage or rubbing
  3. Check the connector for corrosion, moisture and a tight fit; wiggle the harness while watching the scan tool
  4. Remove the sensor and clean off dirt and metal particles
  5. Inspect the tone ring for cracks, missing teeth and rust, and check the wheel bearing for play
  6. Measure sensor resistance and test the wiring to the ABS module for opens and shorts to ground (use specs for your model)
  7. Verify the sensor is seated correctly with the proper air gap
  8. Clear the code and road test to see if it returns

Common fixes

  • Replace the right front wheel speed sensor
  • Repair or replace the damaged wiring or connector
  • Clean or replace the tone ring, or replace the hub bearing if the ring is built in
  • Clean the terminals and seal the connector against moisture
  • Replace the ABS module only after all external causes are ruled out

Questions and answers

Can I drive with code C0033?

Yes, but carefully and not for long. Normal braking works, but ABS and stability control are off, so stopping on slippery roads is riskier.

What most often causes C0033?

Usually the sensor itself or its wiring in the wheel well, such as a broken wire or a corroded connector. A dirty sensor or damaged tone ring can also cause it.

Will clearing the C0033 code fix it?

Clearing it only hides it for a while. If the cause is still there, the code and ABS light will come back soon after you start driving.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.