ABS Wheel Speed Sensor Input Signal Malfunction
Issues with the ABS wheel speed sensor signal detected.
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What it means (plain English)
The ABS system uses wheel speed sensors to monitor how fast each wheel is spinning. If a sensor isn't working correctly, it can't send proper signals to the car's computer, which may cause problems with the anti-lock brake system.
What the computer is actually seeing
The ABS control module looks for a regular signal from each wheel speed sensor, typically a square wave signal with alternating voltage levels representing wheel speed. The expected signal frequency ranges from 0 to 15 Hz when stationary to 50 Hz or more while driving.
What a healthy reading looks like
Voltage changes from 0V to 12V or more; frequency varies based on speed, aiming for 0-15 Hz (stationary) and 50 Hz+ (at speed).
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors for the affected wheel speed sensor; look for frays or corrosion.
- 22. Check the sensor's resistance with a multimeter; it should typically be around 1,000 to 1,500 ohms.
- 33. Test the sensor's output voltage while rotating the wheel; expect voltage changes from 0V to around 5V.
- 44. If the sensor fails any of the above tests, replace it and clear the code. If problems persist, test the ABS control module.
Common causes
- Faulty wheel speed sensor
- Damaged wiring or connectors
- Rust or debris on the sensor
- Faulty ABS control module
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with code C0300?
It's best to repair it soon; braking performance may be affected.
Will this code come back after clearing?
If the underlying issue isn't fixed, yes, it will return.
Why does this code sometimes pair with C0301?
C0301 indicates a fault in the opposite wheel speed sensor, often due to a shared problem like wiring.
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