I am getting COMM ERROR's on my handheld now and then. I have checked the connection between the handheld and ecu. I am not using the extension cord between the handheld and ECU as they are right next to one another, mounted in the glove box. Here are the facts on my situation.. -new build, ~10 miles on testing and tuning -when the COMM ERROR comes up on the screen, the car continues to run as it should, it has never acted up, shutdown, etc. -when the COMM ERROR comes up, the handheld resets itself, sometimes will go to HOME screen until I select Live Data or Advance, etc. then it will either enter those screens or go back to COMM ERROR. -it has never gone from the Live Data screen (which I mostly have on) to COMM ERROR or gone to COMM ERROR during operation, it is always when I try to enter the Live Data or Advance screen from the Home screen. -when I REALLY want to access the advance screen and am getting the COMM ERROR, I just continue letting the ECU reset itself and eventually, when I choose the screen I want (usually Live Data) the screen will come up showing everything operating. It has never gone from this screen to a COMM ERROR. I have tried wiggling plugs, pulling at wiring, etc. The best I can get from the tech line is that there must be a connection issue. I am not convinced this is really a connection issue as the tech line has told me, but I would be happy to find where it is! Here is how I have it wired: -Positive wire to positive of battery in the trunk, Negative to negative side of battery. I had to extend wire length by a few feet (maybe 2-3) and did so by using next size up wire, soldered to the provided power and ground wire. The power and ground wire are run under the passenger side door sill all the way back to the trunk. There are no other wires run along with these wires. -RPM input signal is from MSD 6AL Box, which also powers Autometer 5" Tach. -MSD 6AL mounted under driver's side fender, powered by positive and negative wires run directly to the battery under the driver's side door sill all the way back to the battery. -ECU and handheld mounted in the glove box. -Fan outputs wired to ground on BeCool provided relays, relays powered by 12+ power distribution block. These work fine so far, the only problem I have noticed is one time when I went to check fan on/off values, there was a 110* split between the two. For example, it would say FAN ON: 201 FAN OFF: 091. I thought this was strange, so I shut it down, turned the key back on and got another COMM ERROR which seemed to bring these values back to a more reasonable split (I don't remember what the difference was). -FAST is NOT controlling timing for me. Any other questions anyone would have I would be happy to answer. So far I am happy with the system but the COMM ERROR's are getting annoying, especially when I want to show off how well the system works to other gear heads.. "hey check out the live screen" COMM ERROR!!