How to tell a "fake" ECU from a real one

Middle leg of that regulator chip is ground. It is common to the mounting tang. The mounting tang really should be against a heat sink and grounded also. If this regulator isn't grounded one way or another, and gets 12 volts in, 12 volts goes right through and out on the 3rd leg. The chip doesn't have any ground fault protection in it. Real Time Engineering points out that their solid state IVR has ground fault protection in its circuitry. This ECU should have also but... who knows? Anyway, I have tried to warn everyone who adds one of these regulator chips to their instrument panel. "If you dont add a dedicated ground wire to that instrument panel you damn sure better screw it to the dash before you power it up. There isn't a ground wire in the harness. Only ground path will be though gauges and senders. 12 volts will go that way."