Voltage drop on Tuner Studio compared to ECU

[Shadowen925]

This is my first post here. I've been trying to sort out a problem and the facebook group I was seeking help form hasn't yielded any results.

I am running a Megasquirt 3 Pro. powering a Toyota 1JZ-GTE non-VVT-i single turbo engine. I'm using GM Air and Coolant sensors as well as a 3bar GM MAP sensor. The rest of the sensors are factory. IACV is a 6 wire factory. (Same as found an a toyota 1UZ-FE) The engine has Toyota Yaris/Prius Coil Packs.

Here is the problem I am having:
When I start the car from a cold start. My alternator puts out around 14v. I'm seeing 13.4 or so at my battery. Seeing 13.4v at my fuse box and 13.4v in Tuner Studio when. As I let the car warm up. (driving or idling) the voltage in tuner studio begins to drop. Slowly it falls to around 12.5 or lower.
In the test I did, Tuner Studio reads 12.6v while my fuse box reads 13.4v after the car has completely warmed up. This drop in voltage affects my injector dead time and causes a lean idle. Also, causes misfire under boost while driving.

While TS is reading mid 12v's I have back probed the ECU on the white connector at Pin 13 (pwr ground) and pin 35 (switched power in). Voltage at these pins reads 13.4 while TS still shows mid 12's.
I have checked the 5 power grounds on the grey connector and 1 power ground on the white connector. They are all solid and grounded to the same block.
I have bench tested my Alternator and it was good.
I have installed a brand new battery. (Opt Red Top)
I have checked and tested resistance on my power and ground cables.
I have tested both the internal fuses in the MS3 Pro

The car is a fairly new install, only a few months old. Runs great even at operating temp until the voltage drops enough.

Please help, this seems to be the only issue in reliability and is impeding my tuning.

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[DaveEFI]

First comment would be to sort out why your volts at the alternator and battery are 0.6v apart. I'd expect no more than 0.1v
How is MS powered? Is it powered direct from the battery via a relay switched from the ignition?
A log of a start with a few seconds before starting might be useful too. To see the battery volts before charging starts.

If it's an ordinary self contained alternator rather than an ECU controlled type, I'd expect it to settle down to 13.8v when the battery is fully charged with no other load than the engine electrics.

[Matt Cramer]

Back probe the AMPSEAL 12 volt supply pin to the logic ground pin. (Or you can take the back cover off and check the voltage at the back of the AMPSEAL header.) Check if the voltage is dropping there too or if it is staying constant but the MS3 is showing a false drop. Let me know what you find.

[Shadowen925]

Back probe the AMPSEAL 12 volt supply pin to the logic ground pin. (Or you can take the back cover off and check the voltage at the back of the AMPSEAL header.) Check if the voltage is dropping there too or if it is staying constant but the MS3 is showing a false drop. Let me know what you find.

I believe that was the pin I had back probed in the picture. At any ground It was a constant 13.4v while the TS showed 12.6

[Matt Cramer]

Adjust the battery voltage calibration under Tools to get it to read the right voltage.

[Shadowen925]

Adjust the battery voltage calibration under Tools to get it to read the right voltage.

I've tried that, And that's not the issue. When I start my car, it reads the correct voltage. Reads 13.5v at source and 13.5v back probed into the MS3 power pin and 13.5 in Tuner studio. When I drive the car. Say 10 miles or so and it's warmed up and has been driven for a while the Tuner studio voltage reads around 12.5 while both the source and the back probe into the power pin on the MS amp seal connector read 13.5v

I can slowly watch the voltage go down .1 at a time in tuner studio as I drive the car. Both power cycles and even complete battery disconnect don't change the voltage reading. Only letting the car sit for a while. (I'm assuming cool down) changes it.

Attached is a log.

[Shadowen925]

File was too big.
Link to Log

https://drive.google.com/file/d/0By-OJY ... sp=sharing