I don't know for sure, but I would think the case of the ECU should be grounded, if anything. If it's not grounded, it ought to be "floating" - i.e., not connected to anything.
I'm guessing that something in the 5V circuit inside the ECU is shorted to ground, killing the 5V reference. Sounds like new ECU time, to me.
(If you have Tunercat, you can change the VIN in your replacement. But it'll still need to be flashed with the appropriate tune (which Tunercat can also do.)
I'm guessing that something in the 5V circuit inside the ECU is shorted to ground, killing the 5V reference. Sounds like new ECU time, to me.
(If you have Tunercat, you can change the VIN in your replacement. But it'll still need to be flashed with the appropriate tune (which Tunercat can also do.)