Just as the title suggests, I am testing a modified wiring harness and am having trouble getting the ecu to power up. I have verified the 12v switched line is getting 12V when the key is on. I tested voltages before the ECU adn once plugged in checked continuity on the main fuse. Everything checks out except the ECU actually turning on. I did mange to turn it on from a straight run from the battery so the ECU is fine. I can get pictures of the readings if anyone thinks it may help. Just curious on maybe finding a shortcut to the solution. The only thing I see in the manual is make sure the 12v is clean. I am not sure what they mean. I am ready 12.2v on ignition and straight from the battery.

Let me know thoughts,

Thanks a ton for any help!

 

Check if you have 12V on pin 1B and grounds on 2A,2B,2C,2D.

 

So my 12v instability issues were solved when I plugged in a fuse. I never went back and checked which one because I pulled all but the main fuse for initial power on testing. It was behaving in a very weird way where the ECU or my PI-Dash would try to pull a 12V load and it would drop to 1.5V. All is good now and testing is moving forward!