Code 24, Vehicle Speed Sensor - 4WD With 4L80-E Transmission: Notes

Fig 1: Code 24, VSS Circuit Diagram (4WD With 4L80-E Transmission)

Courtesy of GENERAL MOTORS CORP.

VSS output sensor is a magnetic induction type. Gear teeth pressed on the outside diameter of the output carrier assembly induce an alternating current in the sensor when drive wheels are turning. Since vehicle speed is taken from the transfer case on 4WD vehicles, output speed sensor signal on these units goes directly to PCM. Code 24 will set if gear selector is not in Park or Neutral, engine speed is at least 3000 RPM and output speed is less than 200 RPM for at lease 1.5 seconds.

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

Test verifies VSS voltage at PCM.
Test verifies VSS signal at sensor.