ok this could very well be a dumb question but bare with me

what exactly is your tach reading off of? the reason i ask is, about 4 months ago my tach slowly started to read low at idle, now sitting at idle it reads like it has no power to it, but a tap of the skinny one it will bounces a little bit. Driving down the road it reads MAYBE 200rpm, throw it to the floor it shoots up like a bat outa hell and tops out at about 4500rpm.

sometimes when its warmer out tho it will read slightly closer to reality, but put it to the floor...same deal.... everything else is fine with the truck, runs good, shifts alright, its just driving nuts, go to look down at it and it doesnt work!

any ideas on what would cause this? and how much to fix it?

 

maybe a bad ground somewhere in the harness

 

ill check everything out, its annoying i cant take it anymore

 

From what i understand ur tach reads from the crankshaft position sensor primarily and if that fails it reads from the camshaft position sensor

 

i thought the tach got its signal through the ecm which in turn got its readings from the crankshaft then the camshaft. But anyways this is a problem with the 06's. Not as bad as your case though, they usually just bounce around not completely die but you should start looking into getting a new cluster... They said this fixes it 99% of the time and if its still under warranty go to the dealer and they will cover it. Good luck

 

i took mine to the shop and everthing up to the ecm is fine but the tach is way off if it works at all.

 

i have the same problem it is making me angry and if i have to get a new cluster i'm not going to be happy because mine isnt under warenty anymore

 

I have it too, I have changed the cluster once and it still is a problem. But first time it was all the instruments now its just the tach.

I have 5k left on my war so i better hurry up and get it in to the dealer.

 

yeah, well if i have to get a new cluster im going to have to pay for it cause i am 250 miles over my warranty. it would have been ok if they would have looked at it when i made the appointment at the dealership, BUT for some reason they were closed that day and i had to leave for a 2000 mile trip later that day, and guess what... YEP i went over

 

I seriously think they design stuff to last just til the warranty is up. My '06 did it for a while then came back out of it - knock on wood - did it for about a month and now its been a few months with no issues. Have you checked price on a new cluster? Just wonderin in case i got to get one.