Yeah, I've seen this before. It seems to occur on 203's and 163's exclusively. I've never seen it happen to a 164. The owner finds out about the problem when they go to state inspection. I'm told it's a timing issue between the ME-SFI module and the scan tool. You can try a different scanner.

Sometimes repeated disconnect/reconnect will get it working. In many cases that I've seen it was necessary to replace ME.