Code
C0040
Brakes / ABS
Right front wheel speed sensor circuit malfunction
The ABS module has no valid signal from the right front wheel sensor.
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Most likely causes
- Faulty wheel speed sensor
- Wiring or connector fault
- Bad tone ring
Symptoms you may notice
- ABS/ESP warning light
- ABS may not work
Checks to run
- Measure sensor resistance and signal
- Inspect wiring and tone ring
Tools you may need
Multimeter
Oscilloscope
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.