blkyata

Hello, I recently installed my ms3pro pnp into my miata nb1. I am having a problem where my battery voltage is getting about .6 - .8 less voltage from my tuner studio, I checked my battery with a multimeter and the terminals to see what they were getting which was around the 12.5 range, and my tuner studio was reading about 11.6-11.8. The car will start fine if you jump it, and tuner studio will hold at 14.5 volts, but once it gets shut off the voltage drops slowly. I will attach a video at the end of this via URL. My tuner was telling me I have a bad ground somewhere, but I am not sure about this as I've never had a problem with my battery before I swapped over to Megasquirt for my turbo build (which was right before this).
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Things I've tried:
The only wiring I've messed with is for the radio/cigarette lighter, I checked my wiring and it looked perfectly fine. I also pulled fuses to remove complete power to the radio, ac, room, etc to see if the voltage would match, but still nothing.

I cleaned the ground on top of the throttle body and the one behind the dipstick with some sandpaper, and the battery terminals were tight

I unplugged the fuel pump because I thought maybe that was my issue, and it still was not my issue
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If anyone can lead me in the right direction please do, I need to get this fixed as my tuner wants this to be fixed before he continues tuning my car. This is my daily and I am starting my Spring Semester in a couple days so I need to try and fix this issue to get the tune finished. Any help is greatly appreciated, I also attached my tune file if anyone wants to check it out to see if something is wrong with it.
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LINK TO VIDEO:
https://streamable.com/rumrco
Expires in two days, can reupload video if anyone needs to watch it

Stoffl

Well first off you need to verify if the voltage measured with a multimeter at the relevant ECU pins / ecu harness is the same as shown in Tunerstudio. If not, there's some adaptions you can make in Tunerstudio.

If that measured voltage is differing too much from actual battery/alternator voltage(measured in engine compartment and trunk) then you DO have some wiring or ground issue.