The Vehicle Speed Sensor (VSS) provides a pulsed signal to the ECU, which is critical for calculating vehicle speed, managing idle control, and enabling VTEC engagement.

Signal Characteristics#

The VSS typically operates as a Hall-effect sensor that generates a square-wave signal. As the transmission output shaft rotates, the sensor interrupts a ground signal, creating pulses that the ECU interprets as speed.

• Signal Type: Square wave (0V to 5V or 0V to 12V depending on ECU/chassis).
• Frequency: Proportional to vehicle speed.
• ECU Input: The signal is sent to the ECU to determine speed-dependent fuel maps and VTEC activation thresholds.

Troubleshooting#

If the speedometer is non-functional or the ECU reports a VSS-related error code, perform the following checks:

1. Check Power: Ensure the sensor is receiving 12V ignition power.
2. Check Ground: Verify the sensor has a solid chassis ground.
3. Check Signal Wire: Use a multimeter or oscilloscope to verify the presence of a pulsed signal at the ECU pin while the vehicle is moving.

Warning

A faulty VSS can prevent VTEC from engaging. Always verify VSS functionality before troubleshooting VTEC solenoid or oil pressure issues.

Tip

If the speedometer works but the ECU reports a VSS error, check the continuity of the signal wire between the sensor and the ECU input pin.

Diagnostic Tools#

Use the following tool to identify specific error codes related to speed sensor malfunctions:

Related Wiring#

For specific pinout locations regarding the VSS signal input, refer to the ECU pinout documentation for your specific chassis.

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