Vehicle Speed Sensor
2021 Honda Accord · 1.5L I4 Turbo
Sensor Type
hall-effect
Waveform Type
dc-square
Location
Integrated into transmission output shaft speed sensor on rear of transmission case, driver side near CV axle, or calculated from ABS wheel speed sensors via CAN bus
Pins
3-pin connector
Timebase
20ms/div at low speeds, 5ms/div at highway speeds
Voltage Scale
2V/div
Trigger
2.5V, rising edge
Wiring
Pink (12V power from ECM), Light Green/Red (VSS signal output to ECM pin D14), Black (ground)
Expected Voltage Range
At Idle
0V to 5V
At Higher RPM
0V to 5V
Expected Pattern
Square wave digital signal, frequency increases linearly with vehicle speed, approximately 8000 pulses per mile
Known-Good Waveform
Clean 0-5V square wave with crisp transitions. At 20 mph expect approximately 30-35 Hz, at 60 mph expect 130-140 Hz. Signal should be present whenever vehicle is moving and proportional to speed. Note: 2018-2024 Accord primarily uses calculated VSS from ABS sensors; transmission output sensor serves as backup verification.
Common Failure Patterns
No VSS signal output while driving, speedometer inoperative
Cause: Failed output speed sensor, broken reluctor ring in transmission, open circuit in wiring
Intermittent VSS signal with dropouts or missing pulses
Cause: Worn transmission output shaft bearing causing air gap variation, damaged reluctor teeth, corroded connector pins
Diagnostic Tips
2018+ Accord uses redundant speed measurement - ECM compares transmission VSS against calculated speed from ABS sensors. If only VSS code sets but speedometer works, suspect transmission sensor. CVT models may show slight frequency variance during ratio changes which is normal.
Related Diagnostic Trouble Codes
P0500P0501P0502P0503
Always confirm waveform data with your vehicle's OEM service manual before diagnosing.
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