I've been doing research on test harnesses, and all I've really gathered are that they're useful but prohibitively expensive. There are a couple of threads where people have asked about building/acquiring them, but the replies are always "here's how to not need one".

I'm a senior electrical engineering student and I think it'd be really dope to build one, but it's been pretty impossible to find clear pictures/diagrams etc. of them to figure out exactly how they work. Basically looks like a board connected to ECU plugs, but that's not the most helpful.

So basically,

1. Are they really that useful/what for?
2. Does anyone know of any places where I could get more technical info on them and how they work?

 

It's essentially a custom built bread board with large holes for test probes.

It allows you to touch pins in the connector without poking holes through insulation while still allowing the wire connections to remain intact. The usefulness is due to the holes all being marked with the corresponding wires/pins so you are not trying to isolate a pin in a spaghetti of wire in a connector.

Being an electrical/electronics student I'm assuming you know what a bread board is.

 

!. Useful sure, but probably not financially practical,hence the lack of aftermarket builds. There are 1000s of different ECUs. One size will never fit all.

2. What type of technical info? All you are doing is creating a breakout box for the ECU.

A lot of diagnostics occur through the diagnostic port on modern vehicles and there are several breakout boxes available for that. Perhaps you can contact one of those companies and get details on how to build a BOB and use that info to build your own......