I have a 2003 tahoe. When turning the key it will not start. We check the batt. and it is okay. Lights do not dim when trying to start truck. What could it be

 

Welcome to the Chevrolet Forum. Solenoid maybe? Ignition switch maybe?

 

loose battery cable to the starter
poor ground cable connection
bad starter if its not cranking at all

put a meter on the starter solenoid and have someone crank the engine
if voltage is present at crank the ignition circuit should be okay, be careful being under vehicle should it start...

 

Beofore we can awnser your question need to know is it turning over? Is it clicking? Can you jump it? Could be altenator, battery, or starter.

 

I assumed (my bad) that since he said the lites didn't dim, that the starter wasn't getting voltage.

 

Try to hit the starter with a hammer while someone is turning the key if it starts you need a starter. Try removing the battery cables and check for corrosion on the bolts.

 

Did you get your Tahoe fixed? I have the same problem, it cranks but won't start. Took it to a shop and it started. Now he has it trying to make it not start again. What happen with yours?