2001 EX Speedo stuck - VSS or bad gauge?

While driving down the 405 yesterday my speedometer read 120 and I about crapped. Then I realized I was doing about 70. The needle would go up or down a bit with my speed and when stopped, it says 80mph. Odometer is working fine. How can I tell if this is a VSS problem or instrument or ???
I can get an instrument cluster (used pull) on ebay for $50. Would the swap be a 30 min job or all day? Any help would sure be appreciated. Thanks.

There is a procedure to check the cluster. I would think a defective VSS would give a CE light and messed up shifting if an automatic. ( I could be mistaken )

The cluster is an easy swap. The mileage in the odometer will be whatever the other car had on it when removed.

Yeah, its an automatic. Everything else works great- no lights or erratic behavior anywhere else- just the needle of the speedo. It moves very slow, not erratic or off/on- just mopes like its dragging or mucked up. Where could I find a way to test the cluster or VSS? Thanks for the help and quick reply!

Try resetting the ECU (remove neg battery terminal for a few). Sounds like a faulty speedo sensor. Is this the stock cluster?

It's the stock cluster. I'll try lifting the battery terminal and see what happens. Thanks!

Whats wierd is that the needle is "stuck" on 80MPH when its parked and only starts to move when i hit 45-50 or so then kinda slowly moves. When I come to a stop- it stays on 80. It hasn't moved lower than 80 in 4 days. I'm at work, but at lunch I'll try the battery thing. Thanks.

Lifted the neg terminal while I had lunch. Connected it back up 20 min later and speedo needle is now at 0. Didn't drive yet, but that looks encouraging. I wonder if it was a fluke thing or if this will be a re-occuring problem. Thanks.

just a quick ? what does VSS mean?

just a quick ? what does VSS mean?

Vehicle Speed Sensor