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1G Where is my VSS located?

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1990TSIAWDTALON

Moderator
11,432
8,068
Nov 14, 2013
Independence, Kansas
As the title states, where is the VSS located on a 1992 Talon TSI Auto? I have a P0721 code being thrown and it leads me back to a bad VSS. My Smart100.1 TCU is telling me that the VSS is off by at least 20 mph at actual 50 so it is throwing my shift points out of whack. I have had my dash out but never noticed a VSS, so if anyone has ever dealt with one in a 1g, please give me a bit of advice on where it is and how to replace it.
As always, thanks.
Here is what the software is telling me:
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And here is the "supposed" VSS as pictured at the parts store:
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Thanks for any guidance!!!
 
I'll go out on a limb and say that's not it, and is some "factory image" vss.


The Speed sensor for our cars is a threaded into the trans above the center diff. Other end runs to the gauge cluster
 
I have been all over my 1g Auto and can't seem to find it and the FSM is pointing at the SPEEDOMETER in the dash for the VSS....
Needless to say, I am confused on this gizmo but need to fix it.
Thanks Detroit! I will go back out and check some more in the area you are pointing out.
 
In a 1g the speedo is cable driven. The cable attaches to a piece above the center diff like DetroitStroker said.
The speedo then has a built in reed switch that provides the ECU speed input.
I don't know anything about troubleshooting this though. Maybe it's possible for the cable to slip some, causing the speedo to read low?
 
Our vss has splines similar to the bottom of an old school ignition distributor
 
I see no wires anywhere around the speedometer cable, just the cable and cable end as an old school car would have, so I'm stumped.
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LOL, like an old car. It is an old car.

There is a magnet on the shaft inside the Speedometer gauge and a reed switch mounted in the gauge and opened and closes as the speedometer turns. The gear in the transmission turns the cable and the cable turns the speedometer. There are no adjustments, so are we sure we are talking about the Car's VSS and not some automatic transmission sensor?
 
Code P0721 - Output speed sensor circuit range/performance.
The VSS wire that went to the TCU is where I am tapped in at and when my speedo reads 50 (and its correct), the VSS is telling my shiftbox its 70 something, always higher than the speedo. The shiftbox 100.1 software is where I am getting the code and can clear it but it comes back.
Thanks guys, you are all very helpful and it is making more sense now, just not sure what to do about it. My original TCU had been repaired and lasted about a month then it went limp. I could ignore limp mode with the software, and I do but something is amiss. I had a irratic TPS that was showing up also but I replaced it and the code has never come back for it.
(Scratching bald head).....
:idontknow: This is on my 92 TSI not my 90.
 
Nope. That is 2g only.


What are you talking about?
I have no relevant 2g knowledge so the info I said was based off of parting out 4 1g autos this summer.

As stated and pictured above, it threads in to the trans above the center diff. It will have splines like a distributor. ...for a 1g

If your talking about "wires" from your trans you are talking about the shift solenoids, NSS, kick down, or temp
 
Last edited by a moderator:
Yeah I am going over the wiring harness inputs and I am using Pin 28, Vehicle speed reed switch like Steve is talking about for VSS input to my TCU.
The picture that I have of the VSS from random parts store x has a 2 pin connector, it can't be seen in the picture though. I have read that the 1.8l cars had them on the trans supposedly so I probably am looking at a part I don't have and the reed switch can't be fixed as far as we know, is that correct?
 
What are you talking about? I have no relevant 2g knowledge so the info I said was based off of parting out 4 1g autos this summer.


As stated and pictured above, it threads in to the trans above the center diff. It will have splines like a distributor.


...for a 1g
Unless auto is different than 5 spd on a 1g the part you reference is just a cable mount. The actual speed sensor is in the speedometer.
 
I'm pretty sure I would have a code for it and I don't.
P0721 is the only code I have and thats what I'm trying to fix. I appreciate all of the suggestions and help no matter what.
 
Did this ever get resolved? From looking at the wiring diagrams, the VSS wire on the TCU (pin #40 Yellow/White) is the correct (and only) wire for a VSS in a 1G.
 
Yes, I tapped into the auto wiring harness of the TCU and pulled the signal from there. I am going to change dash assemblies and see if the VSS signal picks up better. I think there have been some upgrades to the VSS signal input on the SmartShift 100.1 shiftbox, if I read their website updates correctly and maybe that is why I was having an issue.
 
Thanks for the update. I just finished installing mine and grabbed the VSS on the TCU. I soldered all the connections...maybe that will slightly help with the signal quality. I saw plenty of bad t-tap connections from my days as a car audio installer.
 
The very latest update version is very neat but my box wouldn't run it so I will need to send it in for a firmware update as mine seems to be one of the first models, no S/N or anything on it LOL. The car it is in is still a month away from running so I really should pull the box and do it but I have no way to test it when I get it back, so I am holding off for a few weeks.
 
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