Code 24, Vehicle Speed Sensor (VSS): Notes

WARNING: This page is about a different car, the 1990 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The speed sensor, which is a Permanent Magnet (PM) generator, provides the control module with vehicle speed information. The PM generator, mounted in the transmission, produces a pulsing voltage signal whenever the vehicle speed is more than 3 MPH. The voltage level and pulses increase with vehicle speed. The control module converts the pulsing voltage to MPH, which is used by the control module in calculations to determine vehicle adjustments.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) A Code 24 will set when MPH reads zero, transmission is not in Park or Neutral, engine speed indicates vehicle is in a cruise mode (1200-4400) RPM, TPS indicates closed throttle and high manifold vacuum is sensed by the MAP sensor. All of these conditions must be met for 2-5 seconds. The PM generator only produces a voltage signal if drive wheels are turning greater than 3 MPH.

Test Number 2) Before replacing the control module, PROM/MEM-CAL should be checked for correct application.