I have 2003 Z71 suburban and the speedometer will not read properly. 90% of the driving time its at 0 mph and the other 10% it reads any where from 5 mph to 120+mph. Any info would help.

 

Your speedo stepping motors are bad. GM has a notice on these and yours may be covered, they have an extended coverage for the 03's. Check you your dealer. If it is not covered, check ebay. You might be able to upgrade to an escalade cluster or just have you existing on rebuild.

 

I had the same problem with the speedometer in my car. I found a website where I had it fixed for $140. They rebuild the entire cluster the guy said that all the gauges in the instument cluster are driven by the same type of motors and that I should replacce all of them before the were out. It made sence to me since the rpm's gauge was beginning to act weird. anyways here is the addres in case you wanna check it out.
http://www.speedometergaugerepair.com