V8 Datsun: Wideband Sensors

One of the reasons I chose the AEM Infinity 708 engine management system is its ability to run two wideband oxygen sensors with internal control.

Wideband sensors sold separately. Obviously. So I got two fresh Bosch LSU 4.2 sensors and guess what?

They don’t plug into the AEM Mini-harness I paid big money for.

Nope.

You need an $85 “adapter harness” to plug the Bosch sensor into the DTM plug on the harness.

$85 EACH.

Not real happy about that, but there’s nothing secret or particularly magical about the adapter, which is just six wires that go from one type of plug to another. So I decided to make my own.

I ordered the two DTM mating plugs I needed to go to the AEM side. That was $3.98. I had the Bosch side connectors from the junkyard harness that had some wire still attached. So I used that.

One of the issues that did need worked out is which wire went where. I spent sort of a long time with wiring diagrams and the ECU pinout to make sure that I was putting the wires in the right place.

Unfortunately I won’t know if it’s right until I fire it up.

I did my best to label everything as clearly as I could, both on the connectors and the wires themselves.

Like I said before, I’m not very impressed with this label printer. Not sure if you can tell here, but it looks like a printer running out of ink. Which it’s not.

Okay, so I wasn’t able to get any in-progress pictures, but I made an attempt at concentric twisting. That means wrapping the wires in a way that provides the most flexibility and smallest cross section possible. There’s a specific way to do it to get everything to lay nicely.

You start with one wire running straight, then you wrap 6 wires around the outside of it, sort of like you see below. The next layer of wires will twist the other direction, and it requires 12 wires to sit nicely. Then the next layer is 18 wires and so on. The number of wires in each layer is so important that real motorsport wiring harness builders will add “filler wires” (wire that isn’t connected to anything) to get the right count.

Well, this particular harness adapter has 6 wires. That means, with 1 center wire and 6 wires for a complete first layer required, I needed to add a filler wire for a total of seven.

But this is just for the stand. It won’t be on the real car build. It’s not getting boots and epoxy and heat-shrink and self-wrapping labels. So give me a break, Phil.

I just made do with what I had to practice. I certainly won’t submit it for judging, but I was pretty happy with how it came out.

This is how it came out before attaching the AEM-side DTM connector: