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Discussion Starter #1
My son has an LLY that the speedo today started showing 35mph plus while stopped for a red light . When moving goes up from there and back down to some other speed shown whn stopped. DIC mileage and odometer seem to be ok. Just speed is all screwed up.
Any ideas of the problem.
Thanks,
aztjc
 

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bad instrument cluster panel. mine went out and is easy to check. Just to verify it isn't your VSS, get to cruising speed and set the cruise control. If the truck holds the speed, then the VSS is bad and tell your dealer to get you an instrument cluster. You'll need to have the mileage, hours and number off the back of the instrument cluster. Be sure to give them the hours with it so the new one comes in with the right data. The dealer will have to program the cluster to match the truck when the new one comes in.
 

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Discussion Starter #3
speedo error

Thanks for the reply.
As of a few minutes ago speedo is stuck at 120+. Will try the cruise.
Should this throw a code?
 

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Discussion Starter #5 (Edited)
speede error

Anyone have a part# or alternate display #? 43k and out of warranty.04.5 D/A, LS chevy

I just did a search and see that this a problem, Should have done this first.
 

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do a search on speedometer repair or instrument cluster and you'll find several places that sell alternative style speedos for the diesels. The part number would be on the back of the speedo. If you pull the front face of the dash off, there are 4 bolts holding in the instrument cluster. While pulling the instrument cluster, rotate it upwards to get to the plug on the back side and un plug it. Then you can pull it completely out. My dealer was able to get mine for $190. Regardless of where you get it, you still have to program the new speedo into the truck. I had to have my dealer do it.

GM is tracking this known issue as well.
 

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NCMIC--My tach and speedo have gone south but when the dealer is open,either I'm not driving or both are working fine so my question is what is the vss you mention? thanks:help:
 

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VSS, variable speed signal. It is one of the leads (pins) on the cluster cable on the back of the cluster. It is the direct input for the speedo potentiometer, among other things.

Ben can point out which one, or go to his DIY nav upgrade thread to find it.
 

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speedo rises while revving engine in park

Anyone ever rev the engine in park and see the speedo move? I was making passes last night to see the performance benefit of the boost stick and during tach cal I noticed that at around 2500rpm and up to 3000rpm while in park my speedo would climb up to like 10mph, maybe even 15mph or so. This is while holding it above and between those rpms.

Whats with that?

.
 

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My old truck with the 454 would do the same thing. My 2005 Trailblazer also does this. I dont know why, but it happens.
 

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At 43k I'd contact your dealer and see if GM will do anything for you, Call their customer care # also. This is a known issue, mine was replaced last year, think at about 26K same problem, speedo peged at 120 while stopped..
 

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I used to work at a Gm dealer...they have always had problems with clusters in all their vehicles..p.s. i had to have mine replace 2 weeks ago (speedo inop)
 
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