C0039 — Right Rear Tone Wheel (Subfault) #

The description of this code may vary depending on the vehicle manufacturer (OEM). Below is a list of known naming variations:

• Right Rear Wheel Speed Sensor Tone Wheel Circuit Malfunction (Ford)
• RR Wheel Speed Sensor Reference Ring Fault (GM/Chevrolet)
• Right Rear ABS Tone Wheel Error (Toyota)
• Rear Right Sensor Tone Wheel Signal Fault (Volkswagen/Audi)

Summary of the C0039 Code #

The C0039 diagnostic trouble code (DTC) relates specifically to the right rear tone wheel—also called the “reference ring”—which is a toothed component attached to the wheel hub or axle. This part works in conjunction with the wheel speed sensor to provide real-time data to the vehicle’s anti-lock braking system (ABS) and traction control system (TCS). A “subfault” indicates the issue is not a total failure, but a specific problem detected in the tone wheel’s performance or signal pattern. When this code is stored, it means the electronic control unit (ECU) has detected irregularities in the signal from the right rear wheel, which can impact both safety features and basic drivability. Addressing this code promptly is crucial for maintaining both vehicle safety and proper ABS function.

Frequent Symptoms for DTC C0039 #

When the C0039 code is present, your vehicle may display a range of symptoms. These commonly affect both driving feel and dashboard alerts. You may notice:

• ABS warning light illuminated on the dashboard
• Traction control system (TCS) or stability control light activated
• Pulsation or vibration in the brake pedal during braking
• Unusual or unpredictable brake behavior on slippery surfaces
• Speedometer fluctuations (in rare cases)

Probable Causes for DTC C0039 #

Like a detective piecing together clues, a technician will look for the most common reasons this code appears. Ranked by likelihood, these include:

1. Damaged or corroded right rear tone wheel (cracks, missing teeth, rust, or physical distortion)
2. Debris or contamination on the tone wheel or wheel speed sensor
3. Faulty or misaligned right rear wheel speed sensor (the sensor reads the tone wheel gaps)
4. Broken or corroded sensor wiring or connector near the right rear wheel
5. Incorrect or non-OEM replacement parts (such as aftermarket wheel bearings or hubs with incompatible tone wheels)

Step-by-Step Diagnosis for C0039 #

Diagnosing the root cause of a C0039 code requires a systematic approach. Here are the recommended steps for a professional or advanced DIYer:

• Scan the vehicle with a professional OBD-II scanner to confirm the C0039 code and check for related ABS or wheel speed sensor codes.
• Visually inspect the right rear wheel area for signs of physical damage, rust, or debris on the tone wheel and sensor.
• Check the sensor wiring and electrical connector for corrosion, broken wires, or loose pins.
• Remove the right rear wheel and brake assembly (if necessary) to gain clear access to the tone wheel and sensor.
• Spin the wheel by hand while watching live data on the scan tool to observe for signal drops or irregularities.
• Test wheel speed sensor output using a multimeter (AC voltage setting) or oscilloscope, comparing readings to the left rear sensor.
• If a fault is found, repair or replace the affected component (tone wheel, sensor, or wiring) and clear the code. Road test to verify the fix.

Possible Repairs for C0039 #

Once you’ve pinpointed the cause, repairs should be targeted and precise. Common solutions tied to the root issues above include:

• Clean the tone wheel and sensor to remove any dirt or metal shavings causing signal interference.
• Replace the right rear tone wheel if damaged, cracked, or missing teeth are found.
• Replace or realign the right rear wheel speed sensor if it’s faulty or mispositioned.
• Repair or replace damaged wiring or connectors in the right rear wheel area.
• Install an OEM-quality (Original Equipment Manufacturer) wheel bearing or hub assembly if previous repairs introduced incompatible parts.

Is It Safe to Drive with the C0039 Code? #

Limited — While you can technically drive with a C0039 code, it’s not recommended for extended periods or in adverse conditions. Your ABS and traction control systems may be partially or fully deactivated, increasing the risk of wheel lockup or skidding on wet, icy, or loose roads. Prompt diagnosis and repair is the wisest route for your safety and to prevent further damage to braking components.

Vehicles Most Commonly Affected by C0039 #

This code appears most often on vehicles equipped with sophisticated ABS systems and individual wheel speed sensors. Models that frequently report C0039 include:

• Chevrolet Silverado, Equinox, and Malibu
• Ford F-150, Explorer, and Escape
• Toyota Camry, Corolla, and RAV4
• Volkswagen Passat, Jetta, and Tiguan
• Buick, GMC, and Cadillac SUVs

Common Mistakes & Best Practices for C0039 #

Missteps during diagnosis or repair can lead to frustration, wasted time, or recurring codes. To avoid the most frequent errors:

• Replacing the wheel speed sensor without inspecting the tone wheel—physical damage to the tone wheel is a leading cause.
• Overlooking corrosion or dirt—even minor debris can disrupt the sensor’s magnetic field.
• Using non-OEM wheel bearings or hubs—tone wheel design varies; use manufacturer-approved parts.
• Neglecting to check wiring and connectors—broken wires are common, especially in snowy or salty climates.
• Forgetting to clear the code and road test—always verify the fix before returning the vehicle to service.

Express FAQ for C0039 #

Quick answers to the most pressing questions about the C0039 code:

• Q: Can a bad right rear tone wheel cause other ABS or stability codes?
  A: Yes, an irregular signal from the tone wheel can confuse the ABS and traction control modules, leading to additional wheel speed or stability control codes.
• Q: Is a tone wheel the same as an ABS ring?
  A: Exactly—“tone wheel,” “reluctor ring,” and “ABS ring” are interchangeable terms for this toothed component used in wheel speed sensing.
• Q: Should I replace the sensor and the tone wheel together?
  A: Only if both are confirmed faulty. Always diagnose each part separately to avoid unnecessary costs.