Just so I understand you, you can communicate with all modules, just not the RCDLR? If thats the case, check the ECM/TCM fuse #11 15amp under hood. Then check the power ckt, connector C1 terminal H, rred and white wire at the RCDLR. Then check the serial data wire C1 terminal L on the RDCLR to the BCM C1 terminal 55, Its a pink wire, make sure its ok.