I swapped an instrument cluster from a 2000 cavalier z24 5sp with a tach into a 2001 cavalier (2.2L) automatic that originally didn't have a tach. Both clusters had digital odometer so the odometer reading stayed, and the tach worked in the 2.2 The gas gauge doesn't work anymore after the swap.
I was under the impression that the fuel sending units were the same in the 00 and 01. Should I put a fuel sending unit from a 99 in the car and see if it works? I'd like to know what will make it work before going through the trouble of dropping the gas tank again.
Thanks!

Fuel sending unit from 2k-2005 is all the same. The 99 one would not read right.

I dont think that swapping clusters would cause it to disable the fuel sender but to check id maybe swap clusters back and see if it works again. That will atleast tell you if the sender is bad or not.

I dont have the original cluster anymore. I swapped it from a wrecked car right before it went to the scrap yard. But the "check gauges" light still comes on when I'm low on fuel, but the needle reads empty, always. I'm positive my gauge read right before the swap in both vehicles.