C101 Plug Question

[randomsv650]

Can't seem to figure this out. I finally got my car running by jumping 12v from the battery junction box on the firewall direct to the coil thankfully!

My problem is somewhere between C101 pin 7 (top side) and the + 15 wire that connects to the coil itself. I need to snip the green wire at the top or C101 and test that for 12v there but I am wondering what that other wire is (smaller, light green) that plugs into pin 7 on C101 top side along with the "big green wire" that runs to the ignition cool. Any ideas? Wondering if this part of my issue.

[jlevie]

Let me see if I have this right. With C101 connected and engine side boot pulled back you have ignition power at pin 7 but not at the coil positive. Correct? If so the engine harness is bad.

You could work around that problem by running a wire from pin 7 to the coil. But without knowing what has happened inside the harness that may run the risk of a harness fire, which could lead to an engine fire.

[randomsv650]

I have full 12v on pin 7 with the plug apart (the "female" pin). When I check pin 7 when the plug is together, from the top of the plug with boot pulled back, I lose voltage and that shows at the coil, so the problem is somewhere between the top portion of the c101 plug and where the coil attaches.

I am just wondering if that additional wire plugged Into pin 7 along with the green wire could have anything to do with it.

[randomsv650]

And when the plug is together and I am checking pin 7 from the engine side (I assume you mean the bottom half of c101) and it shows only 7v. Only when I disconnect and check engine side at pin 7 am I showing 12v.

[toointoxicated60]

measure the resistance in the wire.

sounds like a corroded wire to me.

[randomsv650]

That's what I am wondering. We checked and have continuity in the wire, when not running, but if its corroded it could still drop out when cranking over I would think

[jlevie]

If you see 12v at pin 7 on the body side with C101 disconnected, but significantly less when harness is connected, there is a high resistance in the Hot in Run and Start circuit on the body side of C101. A bad ignition switch would be my first suspect.

[randomsv650]

If you see 12v at pin 7 on the body side with C101 disconnected, but significantly less when harness is connected, there is a high resistance in the Hot in Run and Start circuit on the body side of C101. A bad ignition switch would be my first suspect.

OK. But wouldn't the switch be working correctly if I am getting 12v at all to pin 7? I had assumed the problem would be somewhere after the switch/top of c101 since im getting voltage. I have tried 2 ignition switches, one from a running car and one from mine, that both have the same results. New one couldn't hurt either i guess.

[jlevie]

If there is a high resistance in the Hot in Run and Start circuit, you can see 12v at the pin when there is no load (engine side disconnected). But the voltage will drop when the load is applied.

The odds of two ignition switches having the same failure isn't that great. Use a meter to check the voltage at ignition switch with the load connected. If you have 12v there work towards C101 to find the problem.

[randomsv650]

If there is a high resistance in the Hot in Run and Start circuit, you can see 12v at the pin when there is no load (engine side disconnected). But the voltage will drop when the load is applied.

The odds of two ignition switches having the same failure isn't that great. Use a meter to check the voltage at ignition switch with the load connected. If you have 12v there work towards C101 to find the problem.

Roger that...thank you!

[randomsv650]

If there is a high resistance in the Hot in Run and Start circuit, you can see 12v at the pin when there is no load (engine side disconnected). But the voltage will drop when the load is applied.

The odds of two ignition switches having the same failure isn't that great. Use a meter to check the voltage at ignition switch with the load connected. If you have 12v there work towards C101 to find the problem.

OK so here is what i found. I was playing around, testing different wires, pins, etc. For the life of me, i couldnt find anything that stated what the 2nd green wire coming out of pin 7 (smaller than the big green main wire) was for. So, i snipped it. The ICV stopped buzzing and the main relay clicked off, so now i know it msut have something to do with that.

What's odd is that once that wire was disconnected, i was showing 12v at pin 7 when C101 connected, and even at the coil + end. When i reconnected that little wire with a jumper, the relay clicked, ICV turned on, and voltage immediately drops to 7-8v.

I realize snipping blind is never a good idea, but what the hell right?

[jlevie]

That wire provide the START signal to the DME and when you cut it the DME shut down. But based on what you've said earlier you are looking on the wrong side of C101 for the cause. There is a high resistance in Hot in Run and Start circuit from the ignition switch and that is where you have to look.

[randomsv650]

Ok got it...that makes sense!

[randomsv650]

That wire provide the START signal to the DME and when you cut it the DME shut down. But based on what you've said earlier you are looking on the wrong side of C101 for the cause. There is a high resistance in Hot in Run and Start circuit from the ignition switch and that is where you have to look.

Hi Jim, bumping this old thread because Ive ran into other issues. Figured I had the car running and was working on other stuff now Im back to where I began.

Before I could get the car to run when jumping 12v direct to coil + but now I cant even do that. If it does start, it will start briefly and then die. Anywhere in the system, when I turn the key to on, i immediately have 12.4V and then it will slowly drop to 11.94V with key in the ON position.

Cranking to start reveals it drops to about 8v (this is measuring from a constant 12v source, like under hood or direct off battery). If i measure at the green wire at ignition switch, i get the same result.

Also, my ICV/ECU seem to buzz intermittently which doesn't make sense. CEL light comes on and off.

[jlevie]

Seeing system voltage slowly drop from 12.4v (a battery at 75% charge) to 11.94v with the load from the engine management system suggests a bad battery. That is reinforced by the drop to 8v when the starter load is applied.