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ECU Voltage lower than battery


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I am still in the early stages of my tuning and trying to make sure everything is functioning properly before I fully tune my fuel map. I currently have the car idle and cruise areas safely tuned.

I am running a Gen2 3SGTE in an AW11 with the ST205 PNP G4+ ECU.

I was having inconsistent voltage issues that I attributed to ground issues. I added a second ground to the battery in the trunk and the voltage is holding fairly stable now but I am getting a few different readings depending on where I check,

Ecu voltage in pc link 14.10
Alternator to chassis 14.58
Battery positive to negative 14.58
B+ backprobing to each of the 5 grounds on the ecu connectors 14.48

Is this somewhat normal? I have checked the grounds in the engine bay and they all seem secure. 

I am mostly concerned about the ecu reading lower than what I'm getting at the ECU pins with a multimeter.

Hopefully someone has some experience with this. Thank you.

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I had been using pin 61 as the main power for my tests and probed 1, 14, 23, 26 and 46 as the grounds.

I will test again using 71 as the main 12v power.

I have attached the numbered pinouts I am referencing.

Thanks for your reply



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Ok, pin 71 receives power from the Circut Opening Relay, which gets power from the EFI relay so I will check the voltage along the path and find where it is dropping. 

Thanks for the quick replies and helpful information, I'll update once I've found the cause.

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