I have a 2005 GXP and lately the coolant temp gauge and speedometer are giving incorrect values.
They are both reading much higher than the real temp or speed.
The hud is working fine for the speed , just the speedometer needle that is messed up.
What is the most likely cause of the problem?

any replies are greatly appreciated

how much higher? could it KM/H instead of MPH? because the speedo can read both

The HUD would change to KM/H also would it not? He said the HUD is reading the correct value.

They both change together when you hit the metric button. Quite a few GXP'x here have had stepper motor problems and failures. I sent an email earlier this week to

http://www.ddinstruments.com/product...FUda2godFHMSLA

They rebuild GM gauge clusters with upgraded stepper motors for $199. The Bonneville isn't listed but they say if your Model isn't listed to write them. Sounds like a better choice than buying new with the same weakness.

Sounds like that'* the thing to try.
I sure enjoy driving our GXP- hate seeing things go wrong with it.
Thanks for your replies

Are you running the correct size tires? Northstars normally run 210F to 225F and the rad fans kick on high at 235F. To have a 225F reading is normal.

The GXP LD8 normal is 200.

Thanks for the replies
Tire size isn't the issue , same as it came with from the factory.
The temp gauge pegs itself randomly and instantly( its obviously not running over 260 degrees).... so its not showing actual temp at all
Has to be an electrical problem in the gauge cluster i think :(

I'm just living with it for now- too many other bills to deal with

And that has been one of the GXP'* weak points. Gauges stepper motors going bad in a modular cluster GM refuses to sell individual parts for.

Not if you are sitting in traffic. The fans come on low speed at 224F & hi speed around 230F.

Rolling down the road at 60mph it may maintain 200F.

210F-225F is normal.