A wheel speed sensor from a different position or a non-matching part number has been installed on the left rear hub.; An aftermarket sensor with incorrect internal resistance or signal characteristics was fitted.; The sensor is physically damaged or contaminated, causing its output to fall outside the expected signature.; Wiring harness damage or poor connector pin fit alters the signal enough to mimic a wrong sensor.; The ABS module has been replaced or reprogrammed with incorrect calibration for the vehicle configuration.; A metallic debris buildup or tone ring damage on the left rear hub changes the signal pattern seen by the module.; The sensor is correct but the module's learned values have not been reset after a repair, causing a persistent mismatch.

DTC codes / C06xx · Brakes, steering and suspension / C0665

C0665Left Rear Wheel Speed Sensor B Incorrect Component Installed

This code means the antilock brake system (ABS) module has detected that the left rear wheel speed sensor circuit is receiving a signal from a sensor that does not match the expected part for that position. The module compares the sensor's electrical signature and signal pattern against its stored calibration and flags the mismatch as an incorrect component installed.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

The ABS warning light is illuminated on the dashboard, often accompanied by the traction control and stability control lights.
The driver may notice no other symptoms besides the warning light, especially if the sensor still produces a usable signal.
The ABS system may be disabled, leading to wheel lockup during hard braking on slippery surfaces.
Traction control and stability control systems may stop functioning, reducing assistance during acceleration or cornering.
A diagnostic trouble code may be stored without any drivability complaint, and the vehicle may pass a basic brake inspection.
In some cases, the speedometer or cruise control may act erratically if the affected sensor signal is used for those functions.

Common causes, most likely first

A wheel speed sensor from a different position or a non-matching part number has been installed on the left rear hub.
An aftermarket sensor with incorrect internal resistance or signal characteristics was fitted.
The sensor is physically damaged or contaminated, causing its output to fall outside the expected signature.
Wiring harness damage or poor connector pin fit alters the signal enough to mimic a wrong sensor.
The ABS module has been replaced or reprogrammed with incorrect calibration for the vehicle configuration.
A metallic debris buildup or tone ring damage on the left rear hub changes the signal pattern seen by the module.
The sensor is correct but the module's learned values have not been reset after a repair, causing a persistent mismatch.

How to diagnose and fix it

Connect a scan tool and read all ABS codes to confirm C0665 is current and not history, then record freeze-frame data.
Visually inspect the left rear wheel speed sensor, connector, and wiring for damage, corrosion, or obvious mismatched parts.
Compare the installed sensor's part number and appearance against the original equipment specification for that position.
Measure the sensor's resistance and output signal with a multimeter or oscilloscope and compare to known-good values.
Check the tone ring or encoder on the left rear hub for debris, cracks, or incorrect tooth count.
If a wrong sensor is found, replace it with the correct part for the left rear position and clear the code.
After repair, perform a road test and verify the ABS module accepts the sensor signal and the code does not return.

Why a correct sensor can still set C0665

A sensor that looks identical and fits perfectly can still trigger this code if its internal resistance or signal waveform differs from the original, so part numbers must be verified, not just fitment.
Wiring repairs that add resistance or change shielding can make a correct sensor appear incorrect to the module, so inspect harness repairs before condemning the sensor.
Some ABS modules learn the sensor signature during a initialization drive cycle, and the code may persist until that cycle is completed even after the right part is installed.
Debris stuck to the tone ring or a slightly bent hub can distort the signal enough to be interpreted as a wrong component, so clean and inspect the ring before replacing parts.
This code does not always mean the sensor is wrong; a failing ABS module or corrupted calibration can misreport a good sensor as incorrect.

Can I keep driving with C0665?

You can usually drive the vehicle, but the ABS and stability control systems may be disabled, so allow extra braking distance and avoid slippery or emergency situations until the fault is repaired.

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.