My 2001 Honda Accord 2.3l (F23A1) automatic will not start or run without obd2 device plugged in. I'll start it up with the obd2 device in and soon as I pull it out car dies. It runs great with the obd2 plugged in. Before all this happened I've been getting this random misfire code p1399. I did a valve adjustment and when I crunk the car back up it did fine. Went down the road and all of a sudden gauges started going crazy all my gauges were irractic. I dont know what's going on. I have a brand new main relay in. Still I have to have obd2 device plugged in for it to even start

Has this been the car has always functioned or is this new?
What is the 'device'? Code reader? Insurance data recorder?

It's a knock off elm device. But it's never done this and the cars been running perfect before I did valve adjustment. I think I might have a ground problem. It runs perfect with the obd2 device in just doesnt start with it out or run.

It was the ground on the drivers side of intake manifold it was loose.