just got the Diagun a few weeks ago and I'm getting a "communication error with ECU" when I try to scan for ABS codes and data stream. tried it with 2 different vehicals, 03 GMC sierra and a 04 cavalier, both with the same problem. I'm running the latest GM software, Ver:35.00. I'm able to get into the engine ECU without any problems and also the SRS. I have no problem scanning the ABS with my old Snap On Solus scanner.
