C0135 is a brake and ABS-related diagnostic trouble code that can be a little scary when it pops up, especially if your ABS or traction control lights come on at the same time. The good news is that this code is usually straightforward to diagnose once you understand what it points to. In most cases, C0135 is tied to the front wheel speed sensor circuit, its wiring, or the ABS module’s ability to read that signal. This guide walks you through what it means, symptoms, causes, and how you or your mechanic can fix it.
What Does C0135 Mean?
C0135 is a chassis (C) ABS/traction control code that typically indicates a problem with the left front wheel speed sensor circuit. Depending on the manufacturer, it may be worded as “Left Front Wheel Speed Sensor Circuit Malfunction,” “Sensor Signal Erratic,” or “Open/Short in Left Front Speed Sensor Circuit.”
Your ABS module (or EBCM) constantly monitors wheel speed sensors to control anti-lock braking and traction control. When it detects an abnormal, missing, or implausible signal from the left front sensor compared to the other wheels, it stores C0135 and usually disables ABS and traction control as a safety measure.
Quick Reference
- Code: C0135
- System: Chassis – ABS/Traction Control
- Typical Meaning: Left front wheel speed sensor circuit fault
- Main Symptoms: ABS light on, traction light on, possible speedometer/TC issues
- Risk Level: Reduced braking stability in emergencies
Real-World Example / Field Notes
In the shop, I see C0135 a lot on daily drivers that live in rust-prone areas. A common scenario: you come in with the ABS and traction control lights on after a few days of wet or snowy weather. On a test drive, I’ll see the scan tool showing zero or erratic speed from the left front wheel while the others read normally. Pulling the wheel off usually reveals a cracked sensor harness, corrosion at the connector, or a wheel bearing with excessive play that’s ruining the sensor reading. Fix the wiring or bearing, clear the code, and ABS comes right back.
Symptoms of C0135
- ABS warning light on – The ABS indicator stays illuminated on the dash.
- Traction control or stability light on – “TRAC,” “ESP,” or “ESC” light may also come on.
- Loss of ABS function – Under hard braking, the wheels can lock instead of pulsing.
- Intermittent ABS activation – ABS may kick in at low speeds for no reason.
- Speedometer or cruise issues – Some vehicles may show erratic speed or disable cruise control.
- Pulsation or noise under braking – Feels like ABS engaging on dry pavement at low speeds.
- No obvious driveability change – Normal driving may feel fine until you need emergency braking.
Common Causes of C0135
Most Common Causes
- Failed left front wheel speed sensor – Internal sensor failure, open circuit, or internal short.
- Damaged sensor wiring or connector – Broken wires, chafed insulation, or corroded terminals near the wheel.
- Rust or debris on tone ring/reluctor – Corrosion or debris interferes with the magnetic pickup.
- Worn or loose wheel bearing with built-in tone ring – Excessive play changes the sensor gap and signal.
- Improperly installed replacement hub or sensor – Incorrect gap or wrong part number causing weak signal.
Less Common Causes
- Faulty ABS/EBCM module – Internal failure in the module’s sensor input circuit.
- Previous collision or suspension damage – Bent knuckle or bracket misaligns the sensor.
- Aftermarket modifications – Lift kits, big brake kits, or non-OE hubs affecting sensor alignment.
- Water intrusion – Moisture inside connectors or the ABS module causing intermittent faults.
- Poor ground or power supply to ABS module – Voltage drops can cause false wheel speed faults.
Diagnosis: Step-by-Step Guide
Tools you’ll want: a quality scan tool that can read ABS data, a digital multimeter, basic hand tools, a jack and jack stands, and ideally a wiring diagram for your specific vehicle. Access to freeze-frame or Mode $06 data is helpful but not mandatory.
- Confirm the code and check for companions.
Connect your scan tool, read all modules, and confirm C0135 is present. Look for other ABS or wheel speed codes (C0035, C0040, etc.). Multiple wheel codes may hint at a module or power/ground issue. - Check live wheel speed data.
With the car safely on a road test or on a lift, monitor each wheel speed sensor. Drive slowly and watch for the left front reading to drop out, stay at zero, or jump around while the others look normal. - Perform a visual inspection.
Safely raise the vehicle and remove the left front wheel. Inspect the wheel speed sensor, harness, and connector. Look for cracked insulation, rubbed-through spots, loose routing, or green/white corrosion at the plug. - Inspect the tone ring or hub.
On some vehicles, the tone ring is visible on the axle or hub; others use a magnetic encoder built into the bearing. Check for heavy rust, missing teeth, metal shavings, or a loose/bad wheel bearing. - Check sensor resistance or signal.
Disconnect the sensor and use a multimeter to measure resistance (for passive sensors) or follow the manufacturer spec. An open circuit (OL) or shorted reading usually means a bad sensor. For active sensors, you may check for proper reference voltage and ground. - Wiggle test the harness.
With the sensor plugged in and the key on, gently move the harness while watching live data. If the wheel speed reading cuts in and out, you likely have an internal break in the wiring. - Check wiring continuity to the ABS module.
If the sensor checks out, use the wiring diagram to test continuity from the sensor connector to the ABS module connector. High resistance or an open circuit indicates a wiring fault between the two. - Verify power and ground at the ABS module.
If multiple wheel codes or strange behavior are present, confirm that the ABS module has solid battery power and clean grounds. Voltage drop tests under load are more reliable than simple static checks. - Consider ABS module failure last.
Only after confirming the sensor, wiring, and power/grounds are good should you suspect a bad ABS/EBCM. Some vehicles require dealer-level tools to properly test and program a replacement module.
Pro tip: On vehicles with magnetic encoder bearings, never use a strong magnet or wire brush directly on the encoder surface. You can easily damage the encoded ring and create a permanent C0135 even after replacing the sensor.
Possible Fixes & Repair Costs
Once you’ve pinpointed the problem, repairs for C0135 are usually straightforward. Common fixes include replacing the left front wheel speed sensor, repairing or replacing the sensor harness, cleaning or replacing a rusted tone ring, or installing a new wheel bearing/hub assembly if the encoder is built in. In rarer cases, the ABS module may need replacement and programming.
Typical cost ranges (parts + labor, approximate):
- Wheel speed sensor replacement: $120–$350
- Sensor wiring repair: $80–$250
- Wheel bearing/hub with encoder: $300–$700
- ABS/EBCM module replacement and programming: $600–$1,200+
Costs vary based on vehicle make, parts quality (OEM vs aftermarket), rust/corrosion level, and labor rates in your area. Vehicles that require programming or special bleeding procedures for the ABS system will be on the higher end.
Can I Still Drive With C0135?
In most cases, you can still drive with C0135 without immediate engine damage, but your braking safety is reduced. When this code sets, the ABS and traction control systems usually shut down. Your base brakes still work, but you may lose anti-lock function during hard stops and stability assistance on slippery roads. Short trips to get home or to a shop are usually fine if you drive cautiously, but you should avoid aggressive driving, towing, or high-speed highway runs in bad weather until the issue is fixed.
What Happens If You Ignore C0135?
If you ignore C0135, you risk longer stopping distances and reduced control during emergency braking or on wet, icy, or gravel roads. A failing wheel bearing or severely damaged wiring can also get worse over time, leading to more expensive repairs or even a wheel bearing failure that affects steering and safety.
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
- C0135 almost always points to a left front wheel speed sensor or its circuit.
- The most common causes are a bad sensor, damaged wiring, or a worn wheel bearing/hub.
- You’ll usually see ABS and traction lights, with ABS disabled until the fault is fixed.
- Diagnosis involves checking live wheel speed data, inspecting the sensor and wiring, and testing continuity.
- Repairs typically range from about $120 to $700, depending on what failed and your vehicle type.
- Driving is possible but less safe in emergency or slippery conditions, so don’t delay repairs.
Vehicles Commonly Affected by C0135
C0135 is especially common on many GM vehicles such as Chevrolet Silverado, Tahoe, Suburban, GMC Sierra, Yukon, and various Buick and Pontiac cars that use hub-mounted wheel speed sensors. It also appears on some Toyota and Lexus models (Camry, Corolla, RAV4, Highlander, ES, RX), as well as certain Nissan, Hyundai, and Kia vehicles. Trucks and SUVs that see a lot of road salt, off-road use, or heavy loads tend to develop C0135 more often due to stress on wheel bearings and exposure of the sensor wiring.
FAQ
Can I clear C0135 and keep driving if it goes away?
You can clear C0135 with a scan tool, and sometimes it may not return right away, especially if the issue is intermittent. However, if the underlying problem isn’t fixed, the code and ABS light will usually come back. Treat a returning C0135 as a sign that you need a proper diagnosis, not just a reset.
Is C0135 always the left front wheel speed sensor?
On most vehicles, yes, C0135 refers to the left front wheel speed sensor circuit. A few manufacturers may define it slightly differently, but it is almost always tied to the front wheel speed signal. Always confirm with service information for your specific make and model to be sure.
Can a bad wheel bearing cause C0135?
Yes, a worn or loose wheel bearing is a very common cause. Many modern wheel bearings have the tone ring or magnetic encoder built into the hub. When the bearing develops play, the sensor gap changes, and the ABS module sees an erratic or weak signal, setting C0135.
How do I know if it’s the sensor or the wiring causing C0135?
You’ll need to test both. Start by visually inspecting the harness and connector for damage or corrosion. Then measure the sensor’s resistance or check for proper voltage and signal. If the sensor tests good, perform continuity tests from the sensor connector back to the ABS module. The results will tell you whether the fault is in the sensor itself or in the wiring.
Can C0135 cause my traction control to shut off?
Yes. Traction control and stability control rely on accurate wheel speed data. When the ABS module loses a clean signal from the left front wheel, it usually disables traction and stability systems as a safety precaution. That’s why you often see both the ABS and traction control lights on when C0135 is stored.