Damaged or corroded wiring harness or connector at the left rear wheel speed sensor, often from road debris or moisture intrusion.; Failed left rear wheel speed sensor due to age, heat, or physical damage from road hazards.; Debris, metal shavings, or rust buildup on the sensor tip or the tone ring, preventing a clean signal.; Damaged or missing teeth on the left rear tone ring (reluctor ring) caused by corrosion or impact.; Excessive wheel bearing play or a failing wheel bearing that disturbs the air gap between the sensor and tone ring.; Open or short circuit in the sensor wiring between the wheel and the ABS module, sometimes from a chafed wire.; Faulty ABS control module, though this is less common and should only be suspected after all sensor and wiring checks pass.

DTC codes / C00xx · Brakes, steering and suspension / C0055

C0055Left Rear Wheel Speed Sensor No Signal

Q: What does code C0055 mean?

Left Rear Wheel Speed Sensor No Signal. C0055 means the anti-lock brake system (ABS) module has lost the signal from the left rear wheel speed sensor, so it cannot tell how fast that wheel is turning. The computer sets this code when it sees no alternating voltage or data from that sensor while the vehicle is moving or during a self-test.

C0055 means the anti-lock brake system (ABS) module has lost the signal from the left rear wheel speed sensor, so it cannot tell how fast that wheel is turning. The computer sets this code when it sees no alternating voltage or data from that sensor while the vehicle is moving or during a self-test.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

The ABS warning light stays on continuously while the vehicle is running.
The traction control and stability control warning lights may also illuminate because those systems rely on the same wheel speed signal.
The ABS may deactivate, allowing the wheels to lock during hard braking, though normal braking still works.
A scan tool may show an erratic or zero mph reading for the left rear wheel while other wheels show normal speed.
Often no symptoms besides the warning light, especially if the fault is intermittent or only occurs at certain speeds.
In some vehicles, the speedometer or cruise control may act erratically if the left rear signal is used for those functions.

Common causes, most likely first

Damaged or corroded wiring harness or connector at the left rear wheel speed sensor, often from road debris or moisture intrusion.
Failed left rear wheel speed sensor due to age, heat, or physical damage from road hazards.
Debris, metal shavings, or rust buildup on the sensor tip or the tone ring, preventing a clean signal.
Damaged or missing teeth on the left rear tone ring (reluctor ring) caused by corrosion or impact.
Excessive wheel bearing play or a failing wheel bearing that disturbs the air gap between the sensor and tone ring.
Open or short circuit in the sensor wiring between the wheel and the ABS module, sometimes from a chafed wire.
Faulty ABS control module, though this is less common and should only be suspected after all sensor and wiring checks pass.

How to diagnose and fix it

Use an OBD-II scan tool with ABS capability to confirm code C0055 and check live wheel speed data for the left rear sensor while driving.
Visually inspect the left rear sensor, its connector, and the wiring harness for damage, corrosion, or loose connections; clean and repair as needed.
Remove the sensor and check the tip and tone ring for metal debris, rust, or missing teeth; clean or replace the tone ring if damaged.
Measure the sensor's resistance and compare it to the manufacturer's specification, and check for an AC voltage signal while spinning the wheel by hand.
Check the air gap between the sensor and tone ring with a feeler gauge if adjustable, and verify the wheel bearing has no excessive play.
Perform a wiggle test on the wiring harness while watching live data to catch intermittent opens or shorts, and repair any damaged wires.
If all sensor and wiring tests pass, follow the manufacturer's diagnostic flow for the ABS module, which may require a bidirectional scan tool to command tests or reprogram the module.

What a missing left rear signal really tells you

A common oversight is replacing the sensor without checking the tone ring; a cracked or rusty reluctor ring will destroy a new sensor's signal just as quickly.
Intermittent faults often appear only at certain speeds or after driving over bumps, so live data logging during a test drive is more reliable than a static resistance check.
The left rear sensor shares its signal with the traction control and stability systems, so a code for one system can be triggered by a fault that seems unrelated to braking.
Corroded connectors at the wheel well are a frequent cause on vehicles driven in wet or salty conditions, and cleaning the terminals often resolves the code without parts replacement.
A failing wheel bearing can set this code by altering the air gap, so always check for play and noise before condemning the sensor or wiring.

Can I keep driving with C0055?

You can usually drive the vehicle with this code because normal braking remains functional, but the ABS and stability control systems are disabled, so avoid hard braking or slippery conditions. Have the fault diagnosed soon to restore full safety system operation.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.