Electrical .1 volts on pin 46

sav22rem22

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So I’ve always had code 29 for the vss sensor and ever since I got my car running right this issue has really stood out. The car stalls coming to a stop light. The car was converted from an auto to a manual who knows how long ago and still has an auto trans harness in it. So I bought a manual trans harness and a new vss sensor and a new gear for my speedo.

Since I was already pulling the interior apart in prep for a floor pan repair and subframe connectors I decided to try and finally make my neutral safety circuit work. Before I changed anything though I did a voltage test at pin 46. With key in the on position or cranking there’s like .05 to .1 volts. Is this cause for concern? I unplugged the O2 sensor harness and this didn’t change anything. I’m able to start the car without the clutch in and I’m able to dump codes without the clutch in. I don’t get error code 67. My clutch switch has nothing plugged into it. I know the black connector with the red and blue wires are for the actual start circuit itself but what about the white connector?

I don’t have the new trans harness in yet so I still don’t have the NGS coming out of the T5 hooked up. I would appreciate any help. To sum up my questions, is .05 to .1 volts at pin 46 normal? The computer is disconnected while I do this. What should I do to get the neutral safety circuit in order? Should I plug in the two connections at the clutch pedal before putting in the new harness or should I wait to get the NGS at the transmission plugged in first?
 
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sav22rem22

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6B8ABF00-4E9C-4E48-90C5-5DB7A6E30BAB.jpeg

Okay so I answered my own question about the car being able to start with or without the clutch. The other end of this thing was plugged into the connector that’s supposed to plug into the clutch switch. I’ve never seen this in anyone’s diagrams or pictures the only thing I’ve seen is a little jumper wire in the end of the connector. What even is this? I plugged the white and black connectors in their respective locations and bam now I have to push in the clutch to start the car. I still have a tiny tiny amount of voltage on pin 46. It’s a tenth of a volt. Is that anything I should concern myself with? I’m about to make sure there isn’t 12v while cranking now but other than that everything seems good. Also what exactly is the NGS on the T5 even for? Is it for idle control parameters or something?
 

sav22rem22

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Okay so before I put my computer in I did a few more tests. I tested pin 30. Key on no voltage at pin 30. When cranking pin 30 voltage shot up to 10-11 volts. I unplugged the O2 sensor harness and bam no more voltage at pin 30. I still never had more than .1 volts on pin 46. I reversed all my steps that I did and put the car back to how it was before I touched it today and checked voltage on pin 30 and it still shot up to around 10 volts. So this means it’s been like that for a long long time. Yet my computer shows no signs of being fried. My O2 harness is pinned for an auto since the trans harness is still an auto. Would repinning this fix this issue? Is my computer most likely fried?
 

sav22rem22

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Alright so final update for now. Manual trans harness still isn’t in so the NGS still isn’t hooked up. I repinned the O2 sensor harness and now have no voltage on pin 30 or 46. I’m assuming the reason there’s no voltage on pin 30 at all is because the NGS isn’t hooked up. My car has been able to dump codes, is very drivable, idles great, and isn’t erratic. I’m very confused as to what was going on. So to sum up my final questions and confusions, why wouldn’t my computer be fried if I’ve potentially had voltage on pin 30 for a long time? What is the white connector at the clutch for? Is it safe to hook the computer back up without the NGS connected? Should I look into opening my computer up to make sure pin 46 isn’t cooked (even though it shows zero signs)? In my previous thread of my car idling with the new exhaust that is what my idles like all the time and I assume if my ecu was fried it wouldn’t idle well at all or hardly even run.
 

sav22rem22

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Alright well one more update. So after I verified no voltage to either pin I put the computer back in. While the computer was unhooked I also took the time to put in a new ECT I had sitting around for a while. The car started up and immediately went down to idle. I let it warm up and dumped the codes and I got my normal codes however I got a code 67 this time. When it got done dumping its normal smog codes I pushed in the clutch and started the car. It immediately died. I started it again then it ran its koeo test. However I noticed the car wouldn’t idle up to its normal 1500 RPMs during this time and as a consequence it gave me a code 12. After it gave me all the normal smog codes i blipped the throttle to start the cbt test. Once again the car wouldn’t idle up to its normal 1500 RPMs ( it stayed at like 1000-1200) and about halfway through I must’ve let off the clutch because the test stopped and the car turned off. I also notice now that my car idles very low. Stable but low. I made sure to do all tests regarding voltages with the computer out. The only things that have changed is that I re pinned the O2 sensor harness as it was pinned for an aod and still had aod wiring regarding the clutch switch and I put the appropriate wires onto the clutch switch. The only thing that’s not complete is the NGS and I’m about to change that. Once I verified all voltages were good I put the computer back in. If my computer was fried would I even be able to dump codes? Would the car even run well enough to even be able to do KOEO tests?
 

Mustang5L5

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Pin the o2 harness to match the year and ECU. If it’s a manual trans ECU, pin for a manual

only difference between AOD and manual trans harness is the plug for the NGS on the top of the t5. This plug and the other plug on the clutch pedal switch are wired in parallel. You’ll want both connected

if you suspect your ECU might be fried, remove it and check for continuity between pin 46 and pin 40 and 60. If there is none, the trace might be burned so you’ll want to open the ECU case and inspect
 

sav22rem22

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Feb 6, 2020
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Pin the o2 harness to match the year and ECU. If it’s a manual trans ECU, pin for a manual

only difference between AOD and manual trans harness is the plug for the NGS on the top of the t5. This plug and the other plug on the clutch pedal switch are wired in parallel. You’ll want both connected

if you suspect your ECU might be fried, remove it and check for continuity between pin 46 and pin 40 and 60. If there is none, the trace might be burned so you’ll want to open the ECU case and inspect
So my O2 harness has been pinned for an AOD for a very long time. I have an A9L and the car is an 89 Gt. I just fixed that yesterday. I just checked for continuity between those pins and I’ve got continuity between all of them. I’m just trying to figure out why it’s not fried. I also installed the manual trans harness and got the NGS plugged up finally. Everything seems to work great except that the new vss and new speedo gear didn’t fix my stalling coming to a stop light. Any tests I can do to verify the wiring inside the car itself isn’t damaged? I’m also still getting code 29. I’m worried that the gear inside the transmission is destroyed. Which is very unfortunate because I do not have the means or time to drop the trans just to replace a gear.
 
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Mustang5L5

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Does your speedometer work? If so the gear is fine.

unplug the VSS and stick a jumper in the plug. Test for continuity on pin 3 and 6 on the ECU harness with ECU unplugged. If you don’t have it, you’ll need to start tracing the wiring back to the plug. You can start at the trans harness plug in the drivers kick panel. You can put jumpers on both sides and check for continuity at both ends to see where the break is
 

sav22rem22

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Does your speedometer work? If so the gear is fine.

unplug the VSS and stick a jumper in the plug. Test for continuity on pin 3 and 6 on the ECU harness with ECU unplugged. If you don’t have it, you’ll need to start tracing the wiring back to the plug. You can start at the trans harness plug in the drivers kick panel. You can put jumpers on both sides and check for continuity at both ends to see where the break is
No the speedo hasn’t worked since I got the car. The speedo cable melted by the headers and when I pulled the old vss out the other day I couldn’t turn the gear while it was still attached to the cable. Once I got the cable out I was able to turn the gear. The gear was also missing two teeth. I’m worried that when the cable melted it sized up causing the trans gear to strip. I’ll do some tests a bit later I’m also hoping I didn’t get a bad vss right out of the box
 

sav22rem22

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Well final update for a while. Everything is working 100% fine with no damage to the ecu (somehow) except that my car stalls coming to a stop with the clutch in. All wiring checks out and all signs point to the gear inside the transmission being sheered or shattered when the speedo cable melted and seized up the gear on the vss. I wish it had only destroyed the vss gear. That’s a whole lot of work just for one tiny gear that’s for some reason made of plastic. So my car isn’t very drivable unless I really make an effort to keep it from stalling or I crank the idle stop screw up which kinda defeats the purpose of everything I’ve done so far.
 

Mustang5L5

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If you pull the VSS out, you can somewhat peer into the hole and see the gear on the T5. If you put the rear on jackstands, you can block one side, and use your foot to turn the wheel and spin the driveshaft. That will allow you to inspect the gear.

it’s a tight squeeze but there’s an angle to see up there
 
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sav22rem22

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If you pull the VSS out, you can somewhat peer into the hole and see the gear on the T5. If you put the rear on jackstands, you can block one side, and use your foot to turn the wheel and spin the driveshaft. That will allow you to inspect the gear.

it’s a tight squeeze but there’s an angle to see up there
I’ll have to try that actually. I did try and look into the hole but I couldn’t see anything because of my horrible angle. Thanks
 

Mustang5L5

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I’ll have to try that actually. I did try and look into the hole but I couldn’t see anything because of my horrible angle. Thanks


It's going to vary based on exhaust setup, which crossmember you have, and other minor variations. If it's tough to see, you can try shining a light in there and taking a video. Tough to do all with one person i know.
 

sav22rem22

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It's going to vary based on exhaust setup, which crossmember you have, and other minor variations. If it's tough to see, you can try shining a light in there and taking a video. Tough to do all with one person i know.
Good point. Stock crossmember but just had a brand new off-road h pipe and full exhaust put in which was my issue because I couldn’t angle my body enough to see inside. I’ll be able to stand up under it at work though and I like the video idea. If the gear is busted I’m going to go ahead and pull the trigger on a new clutch anyway because the clutch that’s in the car has my leg shaking by the time I’m out of a drive through lol.
 

sav22rem22

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So a little update again. Haven’t been able to look at the gear at work yet but I have noticed that if I’m going like 55 in 4th gear which would mean I’m turning around 2300 to 2400 and I push the clutch in the car will not stall and will slowly idle down as it’s supposed to. However if I clutch in in let’s say 3rd gear about to come to a stop it will fall on its face. This is confusing
 

sav22rem22

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Well I got around to looking at the gear at work the other day. I wasn’t able to get the rear off the ground to spin the tire or anything to inspect the whole gear but from what I could see it definitely doesn’t look good.
A08EF149-AF48-4FB6-9A70-EC3785612C84.png
 

Mustang5L5

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Yup. The clip broke and the gear slipped.

I always recommend these be discarded and a new one installed because the act of removing them sometimes fatigues the metal and they break or slip. The gear is likely fine, but you might want to have one on hand just in case.

unfortunately you need to pull the tailhousing to fix it
 

sav22rem22

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Yup. The clip broke and the gear slipped.

I always recommend these be discarded and a new one installed because the act of removing them sometimes fatigues the metal and they break or slip. The gear is likely fine, but you might want to have one on hand just in case.

unfortunately you need to pull the tailhousing to fix it
Yeah once I saw that I decided to go ahead and order a new gear and clip. I’m having a bunch of work done soon and am having this gear done as well. What a journey. Also ordered some new carpet with the mass backing so my car doesn’t smell like a retirement home anymore. Also any advice for removing the shifter linkage on the T5? I know there’s a pin that has to be punched out but I’m not too confident on this job