C0401moderate severityChassis
ACC Distance Sensor Circuit
on 2018 Mazda Mazda3 2.5L I4 · FWD
What this code means
General malfunction in the adaptive cruise control distance sensing radar or lidar unit.
Symptoms
- ACC system disabled
- Forward collision alert disabled
- Cruise control limited to non-adaptive mode
- Warning message on dash
Common causes
- Radar/lidar unit failure
- Sensor blocked by dirt or ice
- Wiring damage to sensor
- Control module failure
Diagnostic steps
- Clean sensor face (radar cover or camera lens)
- Check for obstructions in front of sensor
- Test sensor power supply
- Inspect wiring and connector
- Perform sensor self-test with scan tool
Repair notes
Clean sensor area first. Replace radar/lidar unit if internal failure.
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C0021
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C0022
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C0023
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C0024
RR Wheel Speed Sensor Range/Performance
C0025
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C0026
RF Wheel Speed Sensor Circuit Intermittent
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LR Wheel Speed Sensor Circuit Intermittent
C0028
RR Wheel Speed Sensor Circuit Intermittent
C0035
Left Front Wheel Speed Sensor Circuit
C0036
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