Hey Scotty my 2006 Lexus GX470 apparently have a bad ECU. When I put the scanner says "No connection ". I hired a mechanic and he already check de relays, fuse and harness. I took the car to Lexus but they don't want to take it. I'm desperate right now and don't know what to do. I'm military and I'm about to get deploy and my wife is pregnant. What you recommend ?
Check for 12 volts on the OBD connector pin 16 and ground on pin 4. If both there, check pcm connector VERY WELL. If that is good, check gnd and 12 volts on pcm (don't know these pins off the top of my head. If determined good power and ground, take ecm out and find an electronics mos/nec on base and ask them to open it in esd safe environment and look for bad solder joints, particularly the larger ones distributing power and ground.
Or swap with known good pcm and hope something external didn't fry the original one (do a lot of checks on pcm connector to insure 12 volts ain't where it doesn't supposed to be before connecting replacement) and check/reprogram new ecm.
Or find a good indy mech and pay... given your current situation, this is what I'd do given same circumstances. Or if your in Clarksville, Scotty will get you sorted.
Does the car run?
Some interesting forum discussion on this subject:
https://www.my.is/threads/ecu-will-not-communicate-troubleshooting-assistance.508282/