ABS and brakes

C0221 — Right Front Wheel Speed Sensor Signal Missing

Severity: medium Safe to drive

What C0221 means

The ABS control module constantly compares the speed of all four wheels using signals from the wheel speed sensors. C0221 is set when the signal from the right front sensor is missing or drops out. Without it, the module cannot tell whether that wheel is locking up, so it disables ABS and usually traction control as well.

Symptoms

  • ABS warning light on
  • Traction or stability control light on
  • ABS does not activate in hard braking
  • Possible wheel lock-up on slippery surfaces
  • May appear along with C0033 and C0040

Possible causes

  1. Failed right front wheel speed sensor
  2. Open, shorted or corroded wiring or connector at the sensor
  3. Damaged or dirty tone ring (reluctor) on the hub
  4. Worn hub bearing changing the sensor air gap
  5. Faulty ABS control module (less common)

How to diagnose

  1. Scan all codes and watch live data for each wheel's speed
  2. Inspect the right front sensor, harness and connector for damage, corrosion or rubbing on suspension parts
  3. Make sure the sensor is seated and secured and is free of dirt and metal debris
  4. Inspect the tone ring for cracks, missing teeth or buildup
  5. Check the wheel bearing for play
  6. Measure sensor resistance and test the wires for opens and shorts to ground using the manufacturer's specs
  7. Check the signal with a scope while spinning the wheel, if available
  8. If the sensor and wiring are good, check power and ground at the ABS module

Common fixes

  • Replace the right front wheel speed sensor
  • Repair the wiring or replace the damaged connector
  • Replace the hub or bearing assembly with the integrated tone ring
  • Repair or replace the ABS module once it is confirmed faulty

Questions and answers

Can I drive with a C0221 code?

Yes, normal braking still works. But ABS and traction control are off, so stopping distances and wheel lock-up risk increase on slippery roads. Don't put off the diagnosis.

What most often causes C0221?

Most often it is a failed sensor or damaged wiring near the right front wheel. A dirty tone ring or a worn hub bearing can also cause it.

Can I just clear the code?

Clearing it may turn the light off briefly, but the code will return if the fault is still there. Find and fix the cause first.

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.