U1000 ECU Class two Communications Failure

The check engine light came on shortly after I replaced my oil pressure sending unit. Got thirty four codes the primary being U1000 (ECU Class two communications failure). The others relate to the Electronic Brake Control Module (most the codes about ABS circuits) and the Transfer Case Module and 4WD Circuits. Disconnected the negative battery terminal and left it over night to reset the computer, but the check engine light came back on. Replacement computer and modules are expensive and starting bids for diagnostics for the first hour start at $100.00 and it will likely take more than an hour to find where it is coming from with this many codes. Has anyone encountered this before? Is there a more effective way to hone in on the problem? PS. The car runs perfect without signs of trouble.