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Whacked out speedometer

I have a 2004 Impala, the speedometer of which is acting crazy. It works fine most of the time, but periodically it goes up or down of its own accord so I can’t tell how fast I am actually going. At first it seemed to do it when it was damp, but now it doesn’t seem to matter what the environmental conditions are. What’s going on?

Most likely, the Vehicle Speed Sensor (VSS) needs to be replaced, unless your car takes readings from the onboard computer, rather than using a VSS. For your sake, I hope that it is a VSS.

Probably a bad instrument cluster. Very common problem on newer GM products. About $600 to have the dealer swap it out. If the car is running and shifting okay, and the check engine light is off, the VSS is probably okay.

likely the VSS sensor…

The VSS would give other symptoms too. It’s not the VSS, it’s the cluster - common GM problem.

Won’t a bad VSS set a code and turn on the CEL?

That is usually true, but I think that we have all gotten used to people posting symptoms without ever mentioning the significant CEL until much prodding has been done. I have more or less given up on asking for that detail.

How about it tabbott8–is the CEL lit up?

Thanks to all who responded,

My knowledge of parts terminology is nil. What is the CEL?

Check Engine Light



No the check engine light is not lit. An added detail is that sometimes the speedometer goes up so far it pegs at over 120 mph., even when the car is turned off. I can however get it to zero out if I repeatedly turn the key on and off.