OBD-II trouble code
C0237: Rear Wheel Speed Signal Erratic
The ABS module is receiving a jumpy, inconsistent rear wheel speed signal. ABS, traction control, and stability control are usually disabled, but your normal brakes still work.
Quick facts
- System
- Chassis
- Category
- ABS / Wheel Speed
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $450
- DIY difficulty
- Intermediate DIY
What does C0237 mean?
The electronic brake control module (EBCM) reads each wheel's speed many times per second to run ABS, traction control, and stability control. C0237 sets when the rear wheel speed signal is present but erratic — it jumps, cuts out briefly, or reads illogically compared with the other wheels. On many GM vehicles the code sets when the rear speed signal drops out for even a few milliseconds while the vehicle is moving above roughly 12 mph, which is the classic signature of a signal that is intermittently interrupted rather than completely dead.
An erratic signal almost always points to something physical disturbing the sensor's reading rather than a totally failed sensor. The most common culprits are a cracked, rusty, or debris-packed tone (reluctor) ring, a chafed or intermittently open wire, a corroded connector, or an incorrect air gap from bearing play. As the tone ring passes the sensor, a chipped tooth or rust scale makes the signal skip, and the module reports the inconsistency.
Because C-code numbering varies by manufacturer, confirm the exact rear sensor location against your make's service data before replacing parts. When the module can't trust the rear input it disables ABS, traction control, and stability control and lights their warnings, but base hydraulic braking is unaffected — the vehicle still stops normally. A good diagnosis watches live wheel-speed data on a drive, then inspects the tone ring, sensor, and wiring for the intermittent fault.
Common causes
- Cracked, rusted, or debris-packed tone/reluctor ring (chipped or missing teeth)
- Chafed or intermittently open sensor wiring
- Corroded or loose rear wheel speed sensor connector
- Incorrect sensor air gap from wheel bearing play
- Metal debris or contamination on the sensor tip
- Failing rear wheel speed sensor
Symptoms
- ABS warning light on
- Traction control and stability control (ESC) warning lights on
- ABS, traction, and stability features disabled
- Warnings that come and go intermittently, sometimes with a bump or over rough roads
- Normal (base) braking still works
Diagnostic steps
- 1.Scan the ABS module and record C0237 plus any companion wheel-speed codes.
- 2.Watch live wheel-speed data on a test drive and look for the rear reading spiking or dropping out while the other wheels track smoothly.
- 3.Inspect the tone/reluctor ring for cracks, rust scale, chipped teeth, or packed debris.
- 4.Wiggle-test the sensor connector and harness while monitoring the signal to reveal an intermittent open.
- 5.Check the sensor air gap and wheel bearing play, since a loose bearing can make the signal wander.
- 6.Clean or replace the tone ring, repair the wiring/connector, or replace the sensor as indicated, then clear the code and confirm the rear signal is stable.
Repair cost
$100 – $450
Replacing a rear wheel speed sensor typically runs $100-$350 at a shop. Wiring or connector repairs can be cheaper. If the fault is a damaged tone/reluctor ring that is pressed onto the axle shaft or integrated into the wheel bearing, the cost rises because that part must be replaced with the shaft or hub assembly.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with wheel speed sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.