2003 Yukon Denali Mileage computer

My aunt has a 2003 Yukon Denali and is having problems with the mileage computer. The gas gauge works just fine, however when she fills it up, the mileage computer says she can only go 200 miles. Until recently, it would always say she could go 400 miles. Any ideas? The dealership wants to drop the gas tank, claiming it is the sending unit.

If your aunt can live without that toy working, she shouldn’t pay for any work in an attempt to get it fixed.The computer can be rebooted by disconnecting the battery for a few seconds but the radio will need the access code put in later. The mileage computer may get fixed but the radio may never be heard again.