C0033 — Right Front Tone Wheel

Generic OBD-II · all makesChassis

Diagnostic trouble code C0033 indicates a problem with the right front tone wheel (also called a reluctor ring) or its associated wheel speed sensor. The tone wheel is a toothed ring that rotates with the wheel hub; the sensor reads its teeth to determine wheel speed. This code sets when the sensor signal is missing, erratic, or out of range, often due to physical damage or excessive air gap.

Symptoms

ABS warning light illuminated
Traction or stability control warning light on
ABS system may not function properly
Speedometer may read zero or behave erratically
Reduced braking performance in slippery conditions

What causes it — most likely first

1. Damaged or missing tone wheel teeth

The tone wheel may have broken, chipped, or missing teeth due to impact, corrosion, or wear. This is the most common cause of C0034.

2. Wheel speed sensor misalignment or damage

The sensor may be loose, bent, or physically damaged, causing it to lose proper contact or spacing with the tone wheel.

3. Excessive air gap between sensor and tone wheel

If the sensor is not mounted at the correct distance from the tone wheel, the signal may be too weak or intermittent.

4. Wheel bearing failure

A worn or loose wheel bearing can cause the tone wheel to wobble or shift, disrupting the sensor signal.

5. Wiring or connector issues

Damaged, corroded, or shorted wires between the sensor and the ABS module can cause signal loss or noise.

6. ABS module fault (rare)

In very rare cases, the ABS control module itself may be defective, but this is far less likely than mechanical or wiring issues.

How it's diagnosed

Visually inspect the right front tone wheel for missing, chipped, or bent teeth. Use a flashlight and mirror if necessary.
Check the wheel speed sensor for physical damage, secure mounting, and proper air gap (typically 0.3–1.5 mm, refer to vehicle specifications).
Measure sensor resistance with a multimeter; compare to manufacturer specs (usually 1–2 kΩ). Also check for shorts to ground or power.
Inspect the wiring harness and connector for corrosion, breaks, or loose pins. Perform a wiggle test while monitoring the sensor signal.
Raise the vehicle and spin the right front wheel while using a scan tool to observe the wheel speed sensor data. Look for dropouts or erratic readings.
If all above checks pass, test the ABS module by swapping with a known-good module (if possible) or performing a module self-test per service manual.

Code facts & related codes

SystemChassis

StandardizationSAE generic — identical on every make

Frequently asked

Can I drive the vehicle with code C0033?

Yes, you can drive, but the ABS and traction control systems will be disabled. The vehicle will still have normal (non-ABS) braking. Drive cautiously, especially on slippery surfaces.

Do I need to replace the entire wheel bearing assembly to fix this code?

Often yes, because on many vehicles the tone wheel is integrated into the wheel bearing hub. However, some designs allow separate replacement of the tone wheel or sensor. Check your vehicle's service information first.

Is the PCM (engine computer) likely to be the cause of C0033?

No. The PCM is almost never the cause of a tone wheel code. The problem is almost always in the wheel speed sensor, tone wheel, wiring, or wheel bearing. Replacing the PCM for this code is a common misdiagnosis and should be avoided.

Can a bad wheel bearing cause C0033?

Yes. A worn wheel bearing can allow excessive play, causing the tone wheel to wobble or shift relative to the sensor, leading to an erratic or missing signal. Inspect the bearing for play and noise.