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I am connecting with an LC2 WB though the EIO. I want to insure the same reference ground with no ground loops.
1) Does the MPVI Pro SUPPLY ground from the ODB connection to the EIO pin #5? (I think yes.)
2) Will that supplied ground handle 3A current?
3) Or is it OK to connect an additional chassis ground to EIO #5 without causing a gound loop within the MPVI Pro?
After talking to Innovate, they suggest I do keep the WB operating all the time, even when the MPVI Pro is not plugged in. Choice (A) I supply a ground from the same point as I ground the WB to the EIO pin 5. That worries me because I might create a ground loop within the MPVI with one ground coming from the the ODB connection and another coming from the EIO. Choice (B) I ignore pin #5 on the EIO and give the MPVI Pro my WB output without trying to create a common ground. That may produce a bias in the MPVI Pro's interpretation of the WB output, although I believe the bias would be constant so I could program around it.
I went with choice A in my current set up. I was also concerned with the ground loop you mention. Solution:
1) Use a wiring diagram and exploded view of your vehicle to determine where the OBDII port on your vehicle gets its ground. Both grounds come from the same place in my car; a pretty large stud attaching the dash framework to the center tunnel.
2) Install your WB using that same ground point.
3) Use that ground point for pin #5.
With all grounds tied back to the same exact point, overkill on the wiring (18ga), any ground issues are eliminated.
The MPVI EIO ground should not be used to power any devices. It's purpose is to be used as a signal reference ground for inputs you connect.
Agreed with you Keith, I will NOT take pin #5 as ground for powering my WB. But, my WB only has ONE ground attachment. The only way I can create a common ground for the MPVI and my WB signal output is to bridge the chassis ground that does power my WB and the EIO #5 pin. That does create the possibility of a ground loop within the MPVI Pro itself. What does HP Tuners say about connecting EIO pin #5 to a ground source?