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740 Help - Where is this electrical wiring merge point located?

JerryJS8

der Junge
Joined
Sep 12, 2004
Location
Normal Saxony
1991 740 turbo

Got a problem with my MAF and Idle control valve. Every now and then I get the 1-2-1 code, but no real drivability problems. At idle the control valve is lazy. Already renewed ALL the grounds, stripping the wire and soldering on a new connector, now it's the positive leads I'm after.

So in the picture I circled a point that I think might be a weak link causing both problems. Where is that thing located? Anyone already ripped apart a stock wiring harness and can give me a hint?

xgMBFjol.png
 
Well, I think I found the culprit, and I don't know if that spade connector wrapped in electrical tape is supposed to be there...

bQH5S4Jl.jpg


Crusty...

SZjRP7Dl.jpg


...and corroded

LpEtCf1l.jpg


That'll be the first thing I swap when I get back in the garage, but if anyone has a clue, I'd still like to know where that knot is.
 
The official greenbooks do a better job of showing connectors and branching points. If you can find a copy of "TP3908202 940 1995 Wiring Diagrams.pdf" it shows that branch point as "13/41" but doesn't show the location. (A greenbook for your 740 would be best but I didn't have one to check.) I'd guess the branch point is somewhere in the engine harness, and it may vary depending on turbo/non-turbo (MAF and RSR switch sides).

I'd try clipping a volt meter across the power and ground pins at the MAF connector and see what it reads at idle. Try wiggling the MAF/IAC/RSR and bulkhead connector wires and see if the voltage changes.
 
Appreciate the info bobxyz! That file is a good resource.

I found the branching point 13/41, it's behind the glovebox. Page 37 shows the location.

---------------------------------------

I replaced the crusty power supply wire with a fresh one, maybe that'll solve my problems. Otherwise I'll have to get to page 37ening it...

QHAHQqCl.jpg


lBSB2pdl.jpg
 
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