STS strange data link problem

[columbusjo]

I have a 99 STS with @ 85k on the clock. Last weekend the fuel gauge began acting erratic, dropping to empty then back to the actual reading until it is now mostly reading empty but occasionally reading correctly. When I turn the key to acc without starting the engine the gauge reads correctly. Once I start the engine the gauge again becomes erratic. I thought..ok the sending unit was faulty, but today the doors did not lock when put in gear nor did the defrost or door lock buttons work. I pulled the codes and here is what was displayed..AMP U1064, DDM U1066 and U1255, IPC U1066 and
U1255, IPM U1160, PCM U1164, RIM U1096, MSM U1160 and IRC U1060. Strange all would lose communication and trigger a class 2 interface error. I'm hoping one of the fourm experts can identify the root cause of this problem. I also have a RSS C1717 from the right front strut that is fairly consistant. Could that be contributing to the above communication issue? Please help, this fourm was a great help in diagnosing my exhaust lifter issue previously: This is driving me nuts! Thanks in advance for all your help suggestions and comments.

[BobbyV]

I check for an intermittent problem in the serial data circuit (#1807/purple). The various modules will set a loss of communication code for the module failing to acknowledge a buss request.