Note On Intermittent
WARNING: This page is about a different car, the 1992 Cadillac Seville and 1992 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
Manipulate VSS wiring and connectors and verify wiring is not too close to spark plug wires. Code can be caused by an open, short to ground, or short to voltage on circuit No. 400 or 401. Also, check for an open or shorted sensor connector, engine-to-dash connector or PCM connector and a defective sensor. If wiring and connectors are okay, substitute a known good sensor, and retest.