So, I'm almost done with the wiring harness thin-out and have an issue that I'm not sure how to solve and just want to get a bit of insight. I didn't manage to get pictures, but can grab some later if my explanation doesn't make any sense, so stick with me.

There's is a Red-Green wire from one of the ECU plugs that goes to the coolant temp sensor that is the main wire in question. Before it goes far from the ECU, it splits and two of them become shields for other sets of wires. One of those shields is for the throttle sensor wires, and this shield is where it gets weird. Those throttle sensor wires go through the SMJ, right next to throttle sensor wires that go to the AT control unit. When these sets of wires go through the SMJ, the shielding for the two sets switch with each other. So the wire that originally started from the coolant temp sensor is now the shield for the set of wires that end up going to the AT control, which I don't need anymore.

If you're still with me after that, the question becomes how do I deal with that shield? My thinking at this point is when I cut them out of the SMJ, I should swap the shields, but I don't want to mess things up. Any insight into this would be very helpful.

 

Thanks a bunch for reading!

That seems odd. 

SJM? The super junction? No ECU wires should be going through this! 

As for shields, it shouldn’t matter if they crossover with the wire swap - shields are usually grounded so I can’t see an issue with the swap/crossover but that does seem odd. 

Cheers 

Bennie

Hmm...well now I'm very worried. I'm talking about the big plug that has the bolt through it. Referenced as the SMJ on page 10 here https://lib.store.yahoo.net/lib/mroseusa/EA2EJ.pdf. I have a handful of wires going through there, including the throttle sensor wires. I was only slightly paranoid about the shields, I was working under the assumption that they'd be fine swapping. But hearing nothing that I need is supposed to go through there has me wondering just how screwed I am :-/

Should I just start looking for one already done up now? Lol

FYI, I haven't responded because you haven't posted WTF you're working on.

Ah, good call. Swapping a 91 EJ22 from a Legacy 2wd Auto into an 88 GL with the DR 5spd manual. If it's not obvious, this is my first wiring harness job so I'm a bit out of my element. I was figuring I'd be able to make it happen, and seemed to be mostly on track, but now I'm all sorts of paranoid. Very thankful right now that y'all are so helpful.

OK, yes, Engine control wires absolutely go through the SMJ on those.

To be honest, I never worried about the shielding. It should run back to the ECU (and grounded through the ECU), I don't recall noticing that path being broken in a harness thin, but I may have missed it.

 

In practice, I've not found this to be terribly crucial. In one case, on my Loyale, I was having a bad connection between ECU and crank sensor, and I strung 2 pieces of new wire from the ECU to engine harness. It was supposed to be temporary, but I never had an issue, and never changed it (It probably lived for 5 years after that).

Oh whew! Such a relief to know that I'm not totally screwed haha. Good to know about the lack of shielding concern. Like I mentioned, I figured it wasn't the end of the world, but seeing as this is my first harness job it seemed that leaning on the side of extra caution would be best and just give an ask.

Thanks a bunch for getting back to me, as well as the info you've put out there. I wouldn't even attempt this if it weren't for all of that.

On 12/14/2020 at 6:00 AM, Numbchux said:

OK, yes, Engine control wires absolutely go through the SMJ on those.

Interesting @Numbchux. Over here the SJM is cut out and left in the scrap pile. I presumed it would be the same in other markets too.  

Apologies for the bum steer @glife

Cheers 

Bennie