ABS Wheel Speed Sensor
2021 Honda Civic · 1.5L I4 Turbo
Sensor Type
hall-effect
Waveform Type
dc-square
Location
One at each wheel hub - front sensors mount in steering knuckle, rear sensors mount in trailing arm/knuckle assembly behind hub bearing
Pins
2-pin connector
Timebase
10ms/div at 25 mph
Voltage Scale
2V/div
Trigger
2.5V, rising edge
Wiring
White/Blue and White/Yellow (polarity not critical) - colors vary by wheel position
Expected Voltage Range
At Idle
0V to 0V
At Higher RPM
0.2V to 5V
Expected Pattern
Square wave digital signal alternating between approximately 0.3V and 4.7V, 48 pulses per wheel revolution from tone ring
Known-Good Waveform
Clean square wave transitions with sharp rising and falling edges. At 25 mph, expect approximately 80-90 Hz frequency. All four sensors should show identical frequencies when driving straight, with amplitude consistently between 0.3V low and 4.5-5.0V high with no missing teeth or erratic pulses.
Common Failure Patterns
No signal or flat line at any speed
Cause: Failed sensor, damaged tone ring, or open circuit in wiring
Intermittent signal dropouts or reduced amplitude below 3V
Cause: Excessive air gap due to bearing play, debris buildup, or weak sensor output
Diagnostic Tips
Honda active sensors require 12V supply power - verify power and ground before condemning sensor. Front wheel bearing failure is common on 10th gen Civics causing tone ring runout. Compare all four sensor frequencies simultaneously while driving to identify faulty sensor or differential issues.
Related Diagnostic Trouble Codes
C0035C0040C0045C0050
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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