Why do the dashboard lights flicker?

Check for weak or lose body grounds.

Just to add to this one the gas gauge drops to empty?Do the door locks cycle while driving or any other strange things happen?Could have a bad body control module pretty common for those to go bad.

saturntech9: The gas gauge sometimes drops to empty, but then recovers -- but not enough to consistently indicate the actual level of the tank (we watch the odometer to confirm when we really need to fill up). The door locks do NOT cycle while driving.

Jacobandnikolas: Would a bad body ground ONLY effect the dash lights and gas gauge? If so, where should we start looking?

Honestly it sounds like a bad body control module if it was a bad ground to the body control module it would effect a lot more then just dash lights and fuel gauge which the body control module controls.A lot of the bad body control modules i have replaced started out with issues with the fuel gauge locks etc.When there is issues with the fuel sending units effecting the gas gauge it sets a code in the body control module.For fuel level circuit when its the body control module it doesnt set a code for that.

Thanks! We'll go with that . . .

Please have someone diagnose it as a bad body control module before replacing it.You have to take it to the dealer to have it replaced the new one has to be programed with correct mileage calibration file options etc.