Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer thinks the left front wheel is spinning way too fast compared to the other wheels. It's like when you spin one wheel of your toy car really fast, but the others are going slower.
The vehicle's ABS (Anti-lock Braking System) has detected that the signal from the left front wheel speed sensor is higher than expected, indicating a possible issue with the sensor or its circuit.
The left front wheel speed sensor is responsible for sending the speed data of the wheel to the vehicle's ABS module. If the signal is too high, it may indicate a malfunction in the sensor, wiring, or connectors, causing incorrect readings that could affect braking performance.
• ABS warning light on
• Inconsistent braking performance
• Possible loss of traction control
• Faulty wheel speed sensor
• Damaged wiring or connectors
• Malfunctioning ABS control module
ABS: Anti-lock Braking System
OBD-II: On-Board Diagnostics, Second Generation
• Inspect the left front wheel speed sensor and wiring for damage.
• Check the sensor's electrical connections for corrosion or loose connections.
• Test the sensor's signal output with a multimeter or scan tool.
• Replace the faulty wheel speed sensor.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ABS control module if necessary.
• Multimeter
• OBD-II scan tool
• Basic hand tools
$100 - $300
Moderate
• Toyota Camry
• Honda Accord
• Ford Fusion
• Regular maintenance checks on ABS components
• Ensure proper installation of wheel sensors
• Avoid driving through deep water or mud
Sensor Issue
• Do not ignore the ABS warning light.
• Have the vehicle inspected by a professional mechanic if the light comes on.
Check with your vehicle manufacturer for specific warranty coverage on ABS components.
This code is commonly associated with vehicles that have experienced sensor wear or damage over time, especially in harsh driving conditions.
Moderate – While the vehicle is still drivable, the ABS system may not function properly, which could affect braking safety.
Driving with a malfunctioning ABS system can increase stopping distances and reduce control during emergency braking situations.
• Vehicle at operating temperature
• Smooth, level surface
The left front wheel speed sensor is located near the wheel hub assembly on the left front wheel.
Q: Can I drive with the C123B code?
A: While you can drive with this code, it's not recommended as it may affect braking performance.
Q: How do I reset the ABS light after fixing the issue?
A: Use an OBD-II scan tool to clear the code, or disconnect the battery for a few minutes.
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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