Vehicle Speed Sensor
2021 Honda Civic · 1.5L I4 Turbo
Sensor Type
hall-effect
Waveform Type
dc-square
Location
Integrated into transmission output shaft speed sensor on transmission case, driver's side near CV axle
Pins
3-pin connector
Timebase
20ms/div at 30 mph
Voltage Scale
2V/div
Trigger
2.5V, rising edge
Wiring
Pink (12V power), Black (ground), Blue/Yellow (signal output)
Expected Voltage Range
At Idle
0V to 0V
At Higher RPM
0.3V to 5V
Expected Pattern
Square wave pulsing between 0.3V and 5.0V, frequency proportional to vehicle speed, approximately 8000 pulses per mile
Known-Good Waveform
Clean square wave with crisp transitions between low (0.3-0.5V) and high (4.5-5.0V) states. At 30 mph, expect approximately 66 Hz frequency. Signal should be consistent with no missing pulses, and frequency should increase/decrease smoothly and proportionally with vehicle speed changes.
Common Failure Patterns
No output signal with vehicle moving
Cause: Failed sensor, no power/ground supply, or damaged reluctor gear
Intermittent signal or erratic frequency not matching speed
Cause: Contaminated sensor tip with metal debris, excessive gear backlash, or failing sensor electronics
Weak amplitude below 3.5V or slow rise/fall times
Cause: Low supply voltage, corroded connector, or sensor internal degradation
Related DTCs: P0500
Diagnostic Tips
CVT-equipped Civics use this sensor for critical transmission control - failure causes limp mode. Verify 12V power supply from TCM first. Metal contamination from transmission wear is common; inspect sensor tip for debris. Compare with ABS wheel speed sensors to verify actual vehicle speed during diagnosis.
Related Diagnostic Trouble Codes
P0500P0501P0502P0503
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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