Note On Intermittents
Manipulate VSS wiring and connectors and verify wiring is not close too 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 an open or shorted sensor connector, engine-to-dash connector, PCM connector or a defective sensor. If wiring and connectors check out okay, substitute a known good sensor and retest.