^^^^^^ bridge from where? A point close to the TCM? Anywhere along the green wire? I guess the only thing I wonder about is that SPLICE in the diagram and incorporating it into the bridge. I guess I could split it in the engine bay false bulkhead and run it in both directions. To the ECU and the relay.

Just to mention, at some point during all of this I replaced the relay socket all together with pig tail lengths. They were fairly long but did not go into the harness itself.

I can do the inline fuse. If you mean from the tranny harness itself, under the car, I can do that. Seems it's always been in the cards..

 

If you can find the splice EMS29 on the green wire, then from there to B+. The purpose is to eliminate or incriminate one of the two feeds to the starter relay - in this case the 'hot' feed, as NorXKR has suggested.

I've suggested a low-value fuse inline to protect the TCM in the event it doesn't do the switching in the way I'd expect. Remember that the car will crank with the shift in any gear while this bridge in place, so take care. The permanent 'P or N' signal may also confuse the ECM, so keep the bridge in place only for the test - don't drive the car.

Intermittent problems can be a pain to track down. It could be a bad contact on the trans harness plug:- you could bridge from there but I suspect it will be easier to work 'topside' for now.

 

Good morning...

I started out yesterday with a brand new and recently charged (in the hour before working) AGM battery.

I'm pleased to say, I did find the splice. It was/is in the smaller of the two looms in the ECM case and not to far back and down that it is impossible to get to. I didn't have the set up (but will) for the inline fuse. I understand the importance of it so won't try this test until I have it.

Strange things. I seemed to have 12.5 v (B+) on the orange wire EM80-41. Over 12v. On the Green EM80-31 never 12v. Always just under. 11.7, 11.9, 11.8.

More than several times, especially after just installing the battery, the key WORKED and turned the starter. Then, less and less. As key turn worked to crank the starter less and less frequently, as before, I got a clunk as if the starter wanted to engage but wouldn't/couldn't. I measured the Green EM80-31 wire at the ECM connection, at the wire as it went into the relay, then, before and after the splice on all 3 splice wires. All under 12v. Can you believe I could NOT find the 2 6v 30/40amp RELAYS I purchased and wanted to try, smh? Just my "luck"...

I do not have a helper...which makes me look pretty strange out in the NYC streets running around the car, lol

Last night I started going further in the wiring diagram in the direction of the transmission and TCM. I see in the ED a capacitor in the wiring diagram that seems to be allllll about powering the transmission... Looks like that is the direction I'll need to be going in? Looks like the capacitor is outside the trans...? And, if it is responsible for delivery of power to the entire trans, it (if is a problem) is a good thing to know more about anyways I think.

(EDIT) Also, on the orange wire side, EM80-41, the drop to ground - if I saw what I think I saw - happened(s) so fast that I wasn't able to see it in the meter. Unless I missed something or it entirely. My DMM is slow to react? Then, once the car is running - voltage - after a second or two drops off all together.

Crazy maker!!! Actually, it ain't so bad.

I'm just sorry to be bother you all with it - over and over.
I appreciate y'all. Specially you, Michael.
Thank you!



This is figure 5.1 in the ED, 2003 xk



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Wondering if this is the capacitor in the ED?

​​​​​From the photo, if submerged in water, seems there's a possibility it could be effected... interrupting delivery of the full 12v to the trans overall...?

 

It is just there to suppress noise in the electric system, so you can just unplug it and see if it makes any difference.

 

Thanks Nor.... Will do. Also've got to get my hands on the WB wire (B+) to see what's going into the trans I guess.

What I don't understand is how can their be 12.5v on one side of the relay and under 12v on the other. Green comes up 11.xx while Orange is 12.5x. strange.

I parked the car out from of my new apartment thankfully, so going and getting my hands into it will be much easier and quicker....

Drove into work today, top down. Amazing machine!

Gotta pop in some new O2 sensors - and solve this damn starting issue! ASAP

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^^This

Someone posted a picture of this capacitor but I can't find the thread at the moment. It's wired between B+ and ground, so if it went leaky it would take out the fuse (F4 5A) in the engine management fusebox rather than reduce the supply voltage. 81 in the diag goes to B+ via this fuse.

I would expect very little voltage difference between the orange and green wires unless the car is in 'crank' mode. Pull the starter relay and measure the voltages on pins 1 & 2 in the socket against ground. What voltages do you read across pin 1 to ground with the shift in P or N, and then with the shift in, say, D? This should help explain what you're seeing.

 

Yes. I was expecting it to be the same. Even though I had the function of each basically reversed in my head. I'd thought that the switch ground was the green if you remember. I am alright but out of my depth with this. Live and learn I guess.

(Braindead) I haven't shifted out of Park or Neutral while I had the leads in the empty sockets at pin 1 and 2 to see what happens with voltage... Hmm. This is just a guess BUT I would imagine I would still have B+ voltage (proper or improper B+ V) and in P or R the ECM just wouldn't allow a 'switch' to ground... But I'll check and see.

I'm aware that the capacitor is a noise suppressor. I didn't know what the result of one gone bad would be though...

What if it's enough to throw of the over all voltage in the trans BUT not enough to blow the fuse...?

The hunt continues...

 

You have the resistance of the relay coil between the green and orange wires, so if the relay is at rest (i.e. it's not being switched) the voltage across it will be low to zero.

The fuse wire has a certain resistance (otherwise it couldn't heat up and melt), but it's small. You won't see more than a few millivolts across an intact one, so even if the cap went leaky but not enough to blow the fuse, it won't decrease the B+ voltage on the supply to the TCM by more than those few millivolts.