# Whacked out speedometer **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [February 24, 2009, 10:13pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931 "2009-02-24T22:13:21Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![tabbott8](https://avatars.discourse-cdn.com/v4/letter/t/df788c/32.png) [@tabbott8](https://community.cartalk.com/u/tabbott8)\ **Post date:** [February 24, 2009, 10:13pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/1 "2009-02-24T22:13:21Z")
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? ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [February 24, 2009, 10:39pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/2 "2009-02-24T22:39:14Z")
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. ---
**Author:** ![TXdealer](https://avatars.discourse-cdn.com/v4/letter/t/50afbb/32.png) [@TXdealer](https://community.cartalk.com/u/TXdealer)\ **Post date:** [February 25, 2009, 2:54am UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/3 "2009-02-25T02:54:07Z")
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. ---
**Author:** ![redtag](https://avatars.discourse-cdn.com/v4/letter/r/c2a13f/32.png) [@redtag](https://community.cartalk.com/u/redtag)\ **Post date:** [February 26, 2009, 1:30pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/4 "2009-02-26T13:30:42Z")
likely the VSS sensor… ---
**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\ **Post date:** [February 26, 2009, 2:00pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/5 "2009-02-26T14:00:55Z")
The VSS would give other symptoms too. It’s not the VSS, it’s the cluster - common GM problem. ---
**Author:** ![Beadsandbeads](https://avatars.discourse-cdn.com/v4/letter/b/c57346/32.png) [@Beadsandbeads](https://community.cartalk.com/u/Beadsandbeads)\ **Post date:** [February 27, 2009, 12:29am UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/6 "2009-02-27T00:29:26Z")
Won’t a bad VSS set a code and turn on the CEL? ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [February 27, 2009, 12:44am UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/7 "2009-02-27T00:44:38Z")
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? ---
**Author:** ![tabbott8](https://avatars.discourse-cdn.com/v4/letter/t/df788c/32.png) [@tabbott8](https://community.cartalk.com/u/tabbott8)\ **Post date:** [February 27, 2009, 7:23pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/8 "2009-02-27T19:23:59Z")
Thanks to all who responded, My knowledge of parts terminology is nil. What is the CEL? ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [February 27, 2009, 7:26pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/9 "2009-02-27T19:26:12Z")
Check Engine Light ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [February 27, 2009, 8:35pm UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/10 "2009-02-27T20:35:04Z")
+1 ---
**Author:** ![tabbott8](https://avatars.discourse-cdn.com/v4/letter/t/df788c/32.png) [@tabbott8](https://community.cartalk.com/u/tabbott8)\ **Post date:** [February 28, 2009, 12:00am UTC](https://community.cartalk.com/t/whacked-out-speedometer/26931/11 "2009-02-28T00:00:33Z")
Thanks, 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.