OBD-II Generic Error Code C0231: How to Fix It (Subaru ABS Rear Wheel Speed Fault)

Q: Is it safe to drive with error code C0231 active?

Your vehicle will still have normal braking, but the ABS system will be disabled while C0231 is active. This means your wheels can lock up during hard braking, especially on wet or slippery roads. It is safest to avoid high-speed driving or driving in poor road conditions until the fault is repaired. Do not ignore the warning, especially if a failed wheel bearing is also suspected.

Q: What is the most common cause of code C0231 on a Subaru?

The most common causes are a failed or contaminated rear wheel speed sensor, a damaged or corroded wiring harness connector near the rear axle, or a worn wheel bearing hub assembly where the sensor is integrated. Rust and road grime buildup on the tone ring is also a frequent culprit on older Subaru models in northern climates.

Q: Can a bad wheel bearing cause the C0231 ABS code?

Yes. On many Subaru models, the ABS wheel speed sensor is built into the wheel bearing hub unit. When the bearing wears out and develops play, it can shift the tone ring out of alignment with the sensor, causing an intermittent or absent speed signal and triggering C0231. If you notice wheel shimmy, grinding noise, or play when rocking the wheel, inspect the bearing immediately.

Q: How do I know which rear wheel speed sensor is faulty?

An ABS-capable OBD-II scanner will usually specify whether the fault is on the left rear or right rear sensor in the code description or freeze frame data. If your scanner only shows C0231 without a side designation, you can test each rear sensor individually with a multimeter, or watch live sensor data on the scanner while spinning each wheel by hand to see which sensor produces no signal.

Q: How much does it cost to fix error code C0231?

A standalone rear wheel speed sensor typically costs between $20 and $80 for parts, making it an affordable DIY repair. If the sensor is integrated into the wheel bearing hub assembly, the hub unit typically costs $80 to $250. Professional labor adds approximately $80 to $200 depending on the shop rate and vehicle. If the ABS control module requires replacement and programming, costs can rise to $400 or more.

Abstract

Error code C0231 indicates that your vehicle's ABS (Anti-lock Braking System) control module has detected an abnormal or missing signal from one of the rear wheel speed sensors. On Subaru vehicles, this typically points to a faulty wheel speed sensor, damaged wiring, a dirty or damaged tone ring, or a failing ABS control module. Because this fault directly affects your anti-lock braking system, it is considered a high-severity issue — your ABS may be partially or fully disabled until the problem is resolved, which can increase your stopping distance in emergency situations.