fuel data center issue 92 deville

My fuel data center reads 70 mpg, 0.0 gallons used, and L on fuel level no mattert how much gas I have in or how many miles I drive. The error code I get tells me communication problem between bcm and ecm.. my question is:

Is the fuel data center the actual bcm or is there a seperate actual bcm.. if so, where is it and what does it look like?

if the fuel data center is the bcm, I seen a fewon ebay for sale for under 30 bux.. woul;d replacing the fuel data center correct the problem?