Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble reading the speed of the right rear wheel. It's like when your bicycle's speedometer stops working because the sensor is dirty or broken.
The C123A code indicates an issue with the right rear wheel speed sensor, which is responsible for measuring the speed of the wheel and sending this information to the vehicle's computer.
The wheel speed sensor is a critical component of the Anti-lock Braking System (ABS) and Traction Control System (TCS). It provides real-time data on wheel speed, which helps the vehicle maintain stability and control. A malfunction in this sensor can lead to inaccurate readings, affecting the performance of these systems.
• ABS warning light illuminated
• Traction control light on
• Inconsistent speedometer readings
• Faulty right rear wheel speed sensor
• Damaged or corroded wiring or connectors
• Debris or dirt obstructing the sensor
ABS: Anti-lock Braking System, which prevents the wheels from locking up during braking.
TCS: Traction Control System, which helps prevent wheel spin during acceleration.
• Use an OBD-II scanner to confirm the code.
• Inspect the right rear wheel speed sensor for physical damage.
• Check the wiring and connectors for corrosion or damage.
• Clean the wheel speed sensor and surrounding area.
• Repair or replace damaged wiring or connectors.
• Replace the faulty wheel speed sensor.
• OBD-II scanner
• Multimeter
• Socket set
$100 - $300
Moderate
• Toyota Camry
• Honda Accord
• Ford F-150
• Regularly inspect and clean wheel speed sensors.
• Ensure wiring and connectors are secure and free from corrosion.
• Avoid driving through deep water to prevent sensor damage.
Sensor Issue
• Do not ignore the ABS warning light; it can affect braking performance.
• Have the vehicle inspected by a professional if unsure about repairs.
Check with the vehicle manufacturer for warranty coverage on ABS components.
Wheel speed sensor issues have been a common problem in vehicles with ABS systems since their introduction.
Moderate – While the vehicle can still be driven, braking performance may be compromised.
Driving with a malfunctioning ABS can increase stopping distances and affect vehicle control.
• Drive the vehicle at a low speed in a safe area.
• Monitor wheel speed sensor readings with a diagnostic tool.
The right rear wheel speed sensor is located near the wheel hub of the right rear wheel.
Q: Can I drive with a C123A code?
A: Yes, but it's not recommended as it can affect braking performance.
Q: How do I know if my wheel speed sensor is bad?
A: Look for warning lights on the dashboard and inconsistent speedometer readings.
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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