C0033
Right Front Tone Wheel (Reluctor Ring) Fault
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The C0033 code indicates a problem with the right front tone wheel, also known as the reluctor ring. This is the toothed metal ring that works with the wheel speed sensor to measure wheel rotation speed. As the wheel spins, the teeth pass by the sensor creating a pulsing electrical signal — the frequency of these pulses tells the ABS module how fast the wheel is turning. When the tone ring is damaged, the signal pattern becomes irregular and the ABS module sets this code.
Common causes include cracked or corroded tone rings, broken teeth, or heavy buildup of metallic brake dust between the teeth. This is particularly common in regions with road salt, as the ring corrodes from the inside out. You may hear a clicking sound from the wheel area if the ring is cracked and pieces are loose.
To inspect the tone ring, remove the right front wheel and look at the ring on the back of the brake rotor, wheel hub, or CV axle (location varies by vehicle). Look for visible cracks, missing teeth, or heavy debris buildup. Cleaning the ring may resolve the issue temporarily, but a cracked or damaged ring needs replacement. On many vehicles, the tone ring is integrated into the wheel bearing hub assembly, meaning the entire hub must be replaced — this increases the cost but also gives you a new wheel bearing.
Severity
Symptoms
- •ABS warning light illuminated on dashboard
- •Traction control warning light on
- •ABS engaging at inappropriate times during normal braking
- •Clicking or grinding noise from the right front wheel area
- •Stability control system may be disabled
Likely Causes
The tone ring (reluctor ring) is a toothed metal ring that rotates with the wheel hub. It can crack from corrosion, metal fatigue, or impact damage, creating gaps in the tooth pattern that produce an irregular signal the ABS module cannot interpret correctly.
Individual teeth on the tone ring can break off due to corrosion, contact with foreign objects, or during brake service. Even a single missing tooth creates a repeating signal anomaly at each wheel revolution that the ABS module flags as a fault.
Brake dust and metallic particles from brake pad and rotor wear are magnetic and can accumulate on the tone ring teeth, filling the gaps between teeth and making them indistinguishable to the sensor, effectively creating a smooth surface with no signal pattern.
The tone ring is typically pressed onto the hub or CV axle shaft. Corrosion can weaken the press fit, allowing the ring to slip or wobble. A loose ring produces an inconsistent signal pattern that doesn't match actual wheel speed.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the damaged tone ring (may require hub or axle replacement if integrated)
- Clean metallic debris from the tone ring teeth and sensor tip
- Replace the wheel bearing hub assembly (if tone ring is integrated into the hub)
- Reseat a loose tone ring on the axle shaft