Code 24: Vehicle Speed Sensor: Notes

WARNING: This page is about a different car, the 1990 Oldsmobile Cutlass Cruiser, 1990 Oldsmobile Cutlass Ciera, 1990 Oldsmobile Cutlass Calais, 1990 Buick Skylark, and 1990 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The Vehicle Speed Sensor (VSS) is a PM generator type located in the transmission or transaxle. As the vehicle moves, VSS produces an AC voltage signal which is routed to the buffer inside the ECM. In the buffer, the AC signal is changed from a sine wave to a square wave and amplified. The square wave is an on/off pulsed signal. The length of time between pulses determines vehicle speed.

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

Code 24 will set if vehicle speed equals less than 3 MPH when the following conditions occur:
- Engine is running greater than 1000 RPM.
- Vehicle is in high gear.
- No Code 28, 29 or 31 is present.
- All conditions met for 40 seconds.
Before replacing ECM, check MEM-CAL for proper application.