C & K Series 2WD With 4L80-E Transmission

WARNING: This page does not describe the selected car, but rather 25 other vehicles, including the 1992 Oldsmobile Bravada, 1992 GMC Vandura Special, 1992 GMC Vandura, 1992 GMC Value Van, and 1992 GMC Sonoma. However, it is still accessible from the selected car via links, so may be relevant.

VSS output sensor circuit consists of a magnetic induction type speed sensor, Digital Ratio Adapter Controller (DRAC), and wiring. Gear teeth cut in the outside diameter of the rear internal gear induce an alternating current in the sensor when drive wheels are turning. Signal is transmitted to the instrument cluster DRAC where it is converted to a square wave signal which is passed on to the PCM, cruise control, speedometer, and anti-lock brake system. Code 24 will set if gear selector is not in Park or Neutral, input speed is at least 3000 RPM and output speed is less than 200 RPM for at least one second. If input speed sensor is not operational at start-up, this can cause VSS to read zero.

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

Test verifies VSS voltage at PCM.
Test verifies operation of VSS.
Test checks circuits No. 821 and 822 up to the instrument cluster.