I'm doing a B-swap in my EK and I got one of those sketchy ebay wiring harnesses and while going through to make sure its wired correctly, I noticed that the MAP is wired to SG2 (D22) instead of SG1 (D21) and 2 of the other sensors that should be connected to SG1 are connected to SG2. My question is are the two sensor grounds interchangeable, or does the MAP have to be the only sensor wired to SG1 and all other sensors on SG2?

 

A little update, I probed SG1 and SG2 on the ECU and they have continuity so I’m going to assume it’s fine that the wires are mixed up.

 

It’s fine, they are both to the same ground plane. What’s important is that whichever ground wire goes to the MAP sensor is dedicated to only that sensor and runs unbroken through the loom. Same with the 5V wire.

All of the other sensors can share the other ground and 5V bus.

It sounds like you’ve got this figured out though.

The reasoning here is that the the MAP is the most critical sensor in calculating where on the maps the engine is, and it’s also the most sensitive to ground offsets and/or input voltage fluctuations.