Damaged or corroded wiring harness to the right rear wheel speed sensor; Poor electrical connection at the sensor connector or ABS module; Failed right rear wheel speed sensor (internal short or open circuit); Blown fuse or faulty relay supplying power to the ABS module or sensor circuit; Corrosion or damage to the sensor mounting area or tone ring affecting signal; Faulty ABS control module (less common but possible)

DTC codes / C00xx · Brakes, steering and suspension / C003B

C003BRight Rear Wheel Speed Sensor Supply

Q: What does code C003B mean?

Right Rear Wheel Speed Sensor Supply. C003B indicates that the antilock braking system (ABS) control module has detected a fault in the electrical supply circuit for the right rear wheel speed sensor. This typically means the sensor is not receiving the voltage or ground it needs to generate a reliable speed signal, which can disable ABS and traction control functions.

C003B indicates that the antilock braking system (ABS) control module has detected a fault in the electrical supply circuit for the right rear wheel speed sensor. This typically means the sensor is not receiving the voltage or ground it needs to generate a reliable speed signal, which can disable ABS and traction control functions.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

ABS warning light illuminated on the dashboard
Traction control system (TCS) warning light may also be on
Often no symptoms besides the warning light, with normal braking performance
In some cases, the ABS may activate intermittently or at low speeds without cause
Loss of ABS and traction control assistance during hard braking or slippery conditions
Cruise control may become inoperative if it relies on wheel speed data

Common causes, most likely first

Damaged or corroded wiring harness to the right rear wheel speed sensor
Poor electrical connection at the sensor connector or ABS module
Failed right rear wheel speed sensor (internal short or open circuit)
Blown fuse or faulty relay supplying power to the ABS module or sensor circuit
Corrosion or damage to the sensor mounting area or tone ring affecting signal
Faulty ABS control module (less common but possible)

How to diagnose and fix it

Inspect the right rear wheel speed sensor connector and wiring for damage, corrosion, or loose pins
Check the ABS fuse and relay, and verify power and ground at the sensor connector with a multimeter
Measure the resistance of the wheel speed sensor and compare to manufacturer specifications
Perform a wiggle test on the harness while monitoring sensor signal with a scan tool to detect intermittent faults
Replace the right rear wheel speed sensor if it fails electrical tests
Repair or replace damaged wiring harness sections as needed
Clear the code and verify the repair with a test drive, ensuring the ABS light stays off

Don't overlook the simple electrical checks

A common mistake is replacing the wheel speed sensor without first checking the connector for corrosion or water intrusion, which can mimic a failed sensor.
The code can be set by a weak battery or charging system issue that causes low voltage to the ABS module, so always verify battery health.
On some vehicles, a faulty ABS module ground can cause this code even when the sensor and wiring test good.
The right rear wheel speed sensor supply circuit may share a ground with other sensors, so a bad ground can affect multiple systems.
After replacing the sensor, the ABS module may require a calibration or relearn procedure on certain models, so consult the service manual.

Can I keep driving with C003B?

The vehicle remains safe to drive under normal conditions because conventional braking is unaffected, but you should avoid hard braking or slippery surfaces since ABS and traction control may not function. Have the fault diagnosed soon to restore full safety system operation.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.