Going in for another swing at tuning in a week. Need to wire up my second fuel pump to the ECU and figure out some VVT stuff. The instructions for the pump say to ground it to a low side driver at the ECU. Power from a switched source obviously, plenty of those available and doesn't need a dedicated pin, just tapped to an existing switched power wire. But I have several options for a low side drivers and all have differences I don't understand. I noticed most low side drivers on the ECU that are being used by the harness for various outputs already all have different labels. Like VVT is wired to a low side pin C2 on the AEM that says 6A max with a 12v pullup. My tuner had me run it to C22 to try, which is another low side that says 6A max but with "no" pullup. My Boost controller is on another low side driver that says 6A max with "no" pullup.

So basically I am left with a few low side drivers, they are:
C3 Low side 6A max with "no" pullup
C4 Same
C21 Low side 1.7A max "no" pullup
C22 (if I remove the added VVT wire I'm using.) It is a low side 6A max "no" pullup
C41 Is another low side 1.7A max "no" pullup
C42 (used by my boost controller) and is a 6A max "no" pullup

So a few questions. Why was the VVT OCV being used on the only Low side driver with a 12v pullup in the AEM ECU? We have yet to try it on C22 which does not have a 12V pullup. So it seems like a more regular driver. Worth a try.
And which of these is best to run my fuel pump from? Why are some 1.7A max and some 6A max? Why did the instructions say to run my boost controller form C42 which is a 6A max low side driver? Doesn't seem like that device would be pulling any kind of greater amps. I am left with either a 1.7A or 6A max with "no" pullup (whatever that means).

Basically, anyone know where is best to pin the low side drive for the 2nd pump on an AEM infinity 506 ECU. Or how to understand and pick the right driver of the available ones left. And I'm wondering why the heck VVT was the only output using a driver with a 12v pullup. Again, we are gonna try it without 12v pullup on a different driver that says "no" pullup.

 

I found an example from a Supra's fuel pump triggers. They use C-63 as a switched power source which is the ECU's main relayed power source, and C41 as the low side driver. I will pin it that way since c41 is open on my ECU and just jump into the wire going into c63. Still don't know jack, but seems like it will work.

 

Yep I would go for C41 based on what you're saying - should be no meaningful amperage draw, it's just a trigger for the relay for your pump. You will set up the trigger logic in the ECU.

As for your VVTI configuration - A pullup is needed when you don't have a voltage source otherwise available - such as on a 2 prong coolant temp sensor. Not sure on AEM, but on Haltech you can enable or disable the pullup on the output, so if you're thinking that is a problem, maybe you can simply disable it instead of having to repin it.

 

Interesting, as we know the OCV does have it's own power source as it has a power/ground wire going to it and the OEM system activates it that way. I wonder why it was pinned to a lowside with 12v pullup in the harness. Well I am going to try it at on a lowside with no pullup this time around. Not expecting a good outcome sadly. But have to try something new. I feel confident in the 2nd pumps wire up. That was easy enough. This VVT thing is killing me.