ABS and brakes code
C0031: Left front wheel speed sensor signal fault
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $40 | $120 |
| Labor: 0.7 to 1.2 hours × $125 to $175 an hour | $88 | $210 |
| Fees: shop supplies, disposal, diagnostics | $0 | $25 |
| Total, rounded | $120 | $360 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, wheel speed sensor replacement. Which repair your car needs depends on a proper diagnosis.
The ABS computer is not getting a good speed signal from the left front wheel sensor, which is the number GM and some other makes use for that circuit. Some makes use the same number for the signal range or input circuit of that sensor, so confirm the meaning with a scan tool or manual.
- Safe to drive?
- Short trips only
- Most common cause
- Dirty or damaged wheel speed sensor
Normal brakes usually still work, but without ABS help the wheels can lock in a hard stop, so leave extra room and brake early. Get it checked soon.
What you may notice
- ABS light on
- Traction control light on
- Stability control turned off
- Speedometer or cruise control acting up on some cars
Common causes, most likely first
- Dirty or damaged wheel speed sensor
- Broken or chafed sensor wire
- Worn wheel bearing or damaged tone ring
- Corroded connector
- Failed ABS module (less common)
Check this first
Compare live wheel speeds on a scan tool. If the left front reads zero or jumps while the others are steady, check that sensor's wire and plug behind the wheel. Corrosion at the connector is common on older cars.
Other repairs that sometimes fix C0031
| Repair | Typical range, Boston |
|---|---|
| Wheel bearing / hub replacement (one wheel) | $260 to $820 |
| ABS control module repair or replacement | $550 to $1,775 |
| Diagnostic scan (check engine light) | $60 to $290 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
C0031 questions
Can I pass inspection with this code?
In many states a lit ABS light is an inspection failure, but rules vary. Check yours, and fix this before the inspection is due.
Will the brakes still work?
Yes. The standard brakes keep working. Only the anti-lock help is off, so brake gently and early on slippery roads until it is repaired.
Is it just the sensor?
Often, but a bad bearing, a damaged tone ring or a wire chafed at the steering knuckle can do the same thing. A look at the whole wheel area prevents replacing a good sensor.
How much does it cost to fix C0031?
The most common fix, wheel speed sensor replacement, has a typical range of $120 to $360 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- C0035: Left front wheel speed sensor signal fault
- C0040: Right front wheel speed sensor signal fault
- C0045: Left rear wheel speed sensor signal fault
More abs and brakes codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.