Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
Your car uses sensors to know how fast each wheel is spinning. This code means there's a problem with the sensor that checks the speed of the right back wheel. It's like when your bicycle's speedometer isn't working because the wire is broken.
The vehicle's ABS system uses wheel speed sensors to monitor the speed of each wheel. Code C0666 indicates that the sensor on the right rear wheel is not sending a signal, possibly due to a broken wire or a faulty sensor.
The C0666 code is triggered when the ABS module detects an open circuit or a malfunction in the right rear wheel speed sensor B circuit. This can affect the vehicle's ability to accurately monitor wheel speed, which is crucial for the anti-lock braking system (ABS) to function properly.
• ABS warning light on the dashboard
• Inoperative or erratic ABS function
• Inaccurate speedometer readings
• Faulty right rear wheel speed sensor
• Damaged or corroded wiring or connectors
• Faulty ABS module
ABS: Anti-lock Braking System
OBD-II: On-Board Diagnostics II, a standardized system for self-diagnostics in vehicles
• Inspect the right rear wheel speed sensor for damage.
• Check the wiring and connectors for signs of wear or corrosion.
• Use a multimeter to test the sensor's electrical resistance.
• Replace the right rear wheel speed sensor if faulty.
• Repair or replace damaged wiring or connectors.
• Replace the ABS module if necessary.
• OBD-II scanner
• Multimeter
• Socket set
$100 - $300
Moderate
• Chevrolet Silverado
• GMC Sierra
• Cadillac Escalade
• Regularly inspect wheel speed sensors and wiring.
• Keep ABS components clean and free of debris.
• Perform routine maintenance checks.
Sensor Issue
• Avoid hard braking until the issue is resolved.
• Have the vehicle inspected by a professional mechanic.
Check with your vehicle manufacturer for specific warranty coverage on ABS components.
Wheel speed sensor issues have been common in vehicles with ABS systems, often due to exposure to road debris and harsh conditions.
Moderate – While the vehicle may still be drivable, the ABS system may not function properly, affecting braking performance.
Driving with a malfunctioning ABS system can increase stopping distances and the risk of skidding. Address the issue promptly.
• Vehicle parked on a level surface
• Ignition in the 'on' position without starting the engine
The right rear wheel speed sensor is located near the wheel hub of the right rear wheel.
Q: Can I drive with a C0666 code?
A: While you can drive, it's not recommended as the ABS may not function properly, affecting your ability to stop safely.
Q: How do I reset the ABS light?
A: Fix the underlying issue first, then use an OBD-II scanner to clear the code and reset the light.
Pro · Four-system diagnostics
A handheld scanner aimed at engine, transmission, ABS, and airbag diagnostic work.
Chassis and ABS faults usually need a scanner that can read brake-system data directly.
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Universal · Torque wrench
Useful when reassembly torque matters for wheel, suspension, and under-hood fasteners.
Useful when wheel, hub, or suspension hardware needs correct reassembly torque.
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Universal · Drive-on ramps
Helpful for safer access underneath the vehicle during exhaust, EVAP, and underbody inspection work.
Helpful for safer access during underbody inspection work.
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