C0140 is a chassis trouble code that usually points to a problem with a wheel speed sensor signal, most often the right front. When this code sets, your ABS module sees something wrong with the wheel speed data it needs for anti-lock braking and stability control. You might notice an ABS light, traction control light, or even feel odd braking behavior. While your regular brakes usually still work, safety systems can be compromised. Understanding what C0140 means, how it behaves, and how to diagnose it will help you decide whether you can handle it yourself or need a shop.
What Does C0140 Mean?
C0140 is a chassis (C) diagnostic trouble code that typically indicates a right front wheel speed sensor circuit malfunction. The ABS/ESC module is not getting a clean, believable signal from that sensor, or the wiring between the sensor and module has an issue.
Different manufacturers may word it slightly differently (like “Right Front Wheel Speed Sensor Circuit” or “Right Front Wheel Speed Sensor Signal Malfunction”), but the core meaning is the same: the module is unhappy with the right front wheel speed input and disables some safety functions as a result.
Quick Reference
- Code: C0140
- System: Chassis – ABS / Traction / Stability Control
- Typical Meaning: Right front wheel speed sensor circuit fault
- Severity: Moderate – affects ABS/ESC, not basic hydraulic braking
- Common Fix: Replace right front wheel speed sensor or repair wiring
Real-World Example / Field Notes
In the shop, C0140 often shows up after a customer complains that the ABS and traction control lights came on after hitting a pothole, curb, or driving in heavy snow. I’ve seen plenty of cases where the right front wheel speed sensor harness gets stretched, rubbed through, or packed with road salt and debris. On some trucks and SUVs, the sensor is built into the hub assembly; corrosion builds up under the sensor, changing the air gap and causing an intermittent signal. The scan tool will show that wheel reading zero or jumping around compared to the others during a road test.
Symptoms of C0140
- ABS warning light on – the ABS indicator stays illuminated on the dash.
- Traction control or ESC light – stability/traction warning lamps may also come on.
- Loss of ABS function – wheels can lock up in hard braking because ABS is disabled.
- Intermittent warning lights – lights may come and go with bumps, turns, or weather.
- Unusual ABS activation – ABS may pulse at low speeds when it shouldn’t.
- Speedometer fluctuation (rare) – on some vehicles, the speedometer may act erratically.
- Stored traction or stability codes – additional ABS/ESC codes may accompany C0140.
Common Causes of C0140
Most Common Causes
- Failed right front wheel speed sensor – internal sensor failure, open circuit, or short.
- Damaged sensor wiring or connector – chafed, corroded, broken, or stretched harness near the wheel.
- Contaminated or damaged tone ring/reluctor – rust, cracks, or missing teeth affecting signal quality.
- Corrosion at sensor mounting surface – changes the sensor air gap and distorts the signal.
- Improperly installed suspension or brake parts – pinched harness or misaligned sensor after work.
Less Common Causes
- Faulty ABS/ESC control module – internal failure affecting the right front sensor channel.
- Poor ground or power supply to ABS module – voltage drops causing false wheel speed faults.
- Water intrusion in harness – hidden corrosion inside wiring or junctions.
- Aftermarket wheel bearings or hubs – incorrect sensor type or tone ring design for the vehicle.
- ECU software issues – rare; may require a control module update or reflash.
Diagnosis: Step-by-Step Guide
To diagnose C0140 properly, you’ll want a decent scan tool that can read ABS live data, a digital multimeter, a jack and jack stands, and basic hand tools. A service manual or wiring diagram helps a lot. If you’re comfortable with electrical testing and safe lifting procedures, you can do much of this at home.
- Confirm the code and check for companions
Connect a scan tool, read all ABS/ESC codes, and note any related wheel speed sensor or power/ground faults. Clear the codes and see if C0140 returns immediately or only after driving. - Visual inspection of the right front area
Safely raise and support the vehicle. Inspect the right front wheel speed sensor, harness, and connector. Look for broken insulation, rubbing on the tire or suspension, loose clips, or corrosion at the plug. - Check live wheel speed data
Using the scan tool, monitor all four wheel speed sensors while slowly driving or spinning the wheel by hand (if supported). The right front should match the others. If it reads zero, jumps, or drops out, you’ve confirmed a signal issue. - Inspect the sensor and tone ring
Remove the wheel and, if needed, the brake caliper/rotor to see the sensor and tone ring (or encoder ring). Look for rust buildup, cracks, missing teeth, or metallic debris stuck to a magnetic encoder. - Test sensor resistance or output
Unplug the sensor and use a multimeter to check resistance (for passive sensors) or reference voltage and signal (for active sensors). Compare readings to spec from service information. An open circuit or short to ground indicates a bad sensor or wiring. - Wiggle test the harness
While monitoring sensor data or resistance, gently move the harness along its length. If the reading cuts out or fluctuates when you move it, you likely have an internal break or poor connection. - Check wiring back to the ABS module
If the sensor tests good, perform continuity tests from the sensor connector to the ABS module connector. Look for high resistance, opens, or shorts between the two wires. - Verify power and ground to ABS module
Use the multimeter to confirm proper battery voltage and solid ground at the ABS module. Low voltage or bad grounds can cause erratic sensor readings and false codes. - Evaluate ABS module (last resort)
If the sensor, wiring, tone ring, and power/grounds all check out, the ABS control module itself may be faulty. At this point, most DIYers are better off having a professional confirm with advanced diagnostics or Mode $06 data.
Pro tip: On many trucks and SUVs, rust buildup under the front wheel speed sensor changes the air gap and mimics a bad sensor. Removing the sensor, cleaning the mounting surface with a wire brush, and reinstalling it often restores a clean signal without replacing parts.
Possible Fixes & Repair Costs
Repairs for C0140 depend on what you find during diagnosis. A simple harness repair or sensor replacement is common, but sometimes you’ll need a hub assembly or even an ABS module.
- Replace right front wheel speed sensor – typically $75–$250 parts and labor, depending on vehicle and access.
- Repair or replace sensor wiring/connector – usually $100–$300, more if the harness section is long or buried.
- Replace wheel bearing/hub assembly with integrated sensor – often $250–$600 per side, depending on vehicle type.
- Clean rust and debris from sensor/tone ring – if done with other brake work, can be minimal extra cost.
- Replace ABS control module – can range from $500–$1,200+ including programming on modern vehicles.
Typical repair cost ranges are driven by parts design (separate sensor vs. integrated hub), labor time, rust/corrosion level, and whether programming or ABS bleeding procedures are required. Luxury and 4×4 vehicles tend to be on the higher end of the scale.
Can I Still Drive With C0140?
In most cases, you can still drive with C0140, but you’re doing it without full ABS and stability control protection. Your basic hydraulic brakes still work, but the system may allow wheel lockup in a panic stop or reduced control on slippery roads. If the ABS and traction lights are on, drive cautiously, increase following distance, and avoid aggressive braking. If you notice any unusual brake feel, grinding, or pulling, or if multiple warning lights appear, it’s wise to have the vehicle inspected as soon as possible.
What Happens If You Ignore C0140?
Ignoring C0140 means you’re relying solely on your driving skills instead of ABS and stability control to keep you out of trouble in emergency situations. Over time, corrosion or wiring damage can worsen, possibly triggering additional ABS or speed sensor codes. In some regions, an illuminated ABS or traction light can also cause your vehicle to fail safety inspections, forcing repairs later under less convenient circumstances.
Related Codes
- C0194 – Chassis Wheel Speed Signal Plausibility
- C0193 – Traction Control Torque Request Signal Range/Performance
- C0192 – Chassis Wheel Speed Signal Plausibility
- C0191 – Traction Control Torque Request Signal Low
- C0190 – Traction Control Torque Request Signal
- C0189 – Brake Wheel Speed Signal Plausibility
- C0188 – Stop Lamp Switch Circuit Range/Performance
- C0187 – Brake Wheel Speed Signal Plausibility
- C0186 – Chassis Wheel Speed Sensor Circuit Fault
- C0185 – Chassis Wheel Speed Signal Plausibility
Key Takeaways
- C0140 almost always points to a problem with the right front wheel speed sensor circuit.
- Common causes include a bad sensor, damaged wiring, corrosion, or a worn hub/tone ring.
- ABS and traction lights will usually be on, and ABS/ESC functions are disabled.
- Diagnosis involves visual inspection, live data comparison, and basic electrical testing.
- Repairs typically range from a simple sensor replacement to a more expensive hub or ABS module.
- Driving is usually possible, but braking safety is reduced, especially in emergencies or poor weather.
Vehicles Commonly Affected by C0140
C0140 is especially common on vehicles from manufacturers that use this style of chassis code, including many GM (Chevrolet, GMC, Buick, Cadillac), Toyota (Toyota, Lexus), and some Nissan and Hyundai/Kia models. You’ll often see it on trucks and SUVs such as Chevy Silverado, GMC Sierra, Toyota Tacoma, 4Runner, Highlander, and similar platforms that see a lot of road salt, off-road use, or heavy loads. Front-wheel-drive sedans and crossovers from these brands can also experience C0140 when front hub bearings or sensors start to fail.
FAQ
Can I clear C0140 and keep driving without fixing it?
You can clear the code, but if the underlying problem is still there, C0140 will usually return quickly. Clearing it does not restore ABS or traction control; the system will disable itself again as soon as it sees the bad signal. It’s better to diagnose and repair the cause rather than repeatedly erasing the code.
Is C0140 always the right front wheel speed sensor?
On most vehicles, yes, C0140 refers specifically to the right front wheel speed sensor circuit. However, some manufacturers use slightly different naming or mapping, so it’s smart to confirm with service information for your exact year, make, and model. The scan tool’s wheel speed data is the best way to verify which wheel is misbehaving.
How do I know if the sensor or the hub bearing is bad?
If the sensor is separate, you can test its resistance and inspect the tone ring. If the sensor is integrated into the hub, you often have to replace the whole hub assembly when the sensor or encoder fails. Excessive wheel bearing play, grinding noises, or visible damage to the encoder ring usually point to a bad hub. Clean electrical tests but erratic speed readings often indicate an internal hub issue.
Can a bad wheel alignment or suspension work cause C0140?
Alignment itself won’t cause C0140, but suspension or brake work done incorrectly can. If the harness is left unclipped, pinched, or routed wrong after repairs, it can rub through or get stretched when you steer, leading to intermittent sensor failures. Whenever C0140 appears right after recent work, recheck the area that was serviced.
How urgent is it to fix C0140?
It’s not usually an immediate “park it now” emergency, but it is a safety issue. Without ABS and stability control, your stopping distance and control on wet or icy roads can be worse. Plan to diagnose and repair C0140 soon, especially if you regularly drive in bad weather, heavy traffic, or at highway speeds.