Speedometer and speed sensor question

[Wizbangdoodle]

I've got another loose end to tie up.

I have driven my car a couple of times, and so far all is well...except the speedometer. I get no indication of speed on the speedometer. I thought it might need a calibration, but I did that today and still the same thing. I checked my wiring on the speedo and it all checks out according to the wiring schematic. I have the TKX 5 speed, so whatever sensor those come with, which plugged straight into the harness. I also have the standard Autometer gauges. All other gauges work, including the tach.

Now I'm wondering if the sensor could be bad. When I did the calibration, the odometer is supposed to show a number that is the number of pulses seen. That number was at 0 the whole time. So, obviously, I'm getting no signal to the speedo. I'm thinking bad sensor or bad wiring.
Anyone have a way to test the sensor? I also noticed that the 2 wires on the sensor are green and gray. At the speedo, the green wire is used and the gray is for speedo EFI return, which is not used. Do I have something wired up wrong? I was thinking I could hook up my O-scope and check for signal coming out of the sensor, but not sure if that will work. Appreciate any help.

[Sharris2]

You don't t have a GPS signal from the sensor. Is it located in a spot open; not covered by metal?

[TrackDay17]

You don't t have a GPS signal from the sensor. Is it located in a spot open; not covered by metal?

The standard Autometer gauges aren't gps I believe.

[PNWTim]

If you are using VSS there is no signal unless the car is moving. The transmission must be turning to generate the signal.

[Steve1979]

I could be way out in right field on this. I haven’t work with a TKX before, so I’m not sure how they are setup internally, but have you taken out the speed sensor to see if it even came with a gear attached? Some speed sensors that I have bought and seen don’t come with one, because the gear needed depends on your setup.

[Wizbangdoodle]

You don't t have a GPS signal from the sensor. Is it located in a spot open; not covered by metal?

No GPS on this unit.

The standard Autometer gauges aren't gps I believe.

This is correct.

If you are using VSS there is no signal unless the car is moving. The transmission must be turning to generate the signal.

During calibration, the car is moving. I drove it for over 2 miles.

I could be way out in right field on this. I haven’t work with a TKX before, so I’m not sure how they are setup internally, but have you taken out the speed sensor to see if it even came with a gear attached? Some speed sensors that I have bought and seen don’t come with one, because the gear needed depends on your setup.

Interesting thought. I'm not sure how I'm going to check this, because the sensor is very difficult to get to. I may end up calling tremec and ask them.

[Dgc333]

There are two wires from the sensor, green and grey. Up in the dash harness the green wire attached to the speed input of the speedo. They grey wire is grounded. Do you have the grey wire grounded?

[edwardb]

I assume you're using the internal VSS on the RH side of the TKX. Very unlikely it's bad. The two wires from the TKX VSS are high signal and low signal. Typical for non-GPS speedos is green wire to the "IN" connection on the speedo and grey to ground. Hopefully that's the case for yours. Although I've often heard from others it doesn't matter. Just so one side is grounded. This has come up before and it usually solves the problem you're describing.

The mechanical VSS location on the LH side is typically not used unless you need a mechanical speedo cable - who does that any more - or some other unique reason. The transmission comes with that location covered and should stay that way in your case.

[rich grsc]

I could be way out in right field on this. I haven’t work with a TKX before, so I’m not sure how they are setup internally, but have you taken out the speed sensor to see if it even came with a gear attached? Some speed sensors that I have bought and seen don’t come with one, because the gear needed depends on your setup.

There are NO gears on the speed sensors on new transmissions.

[JohnnyDeere]

I assume you're using the internal VSS on the RH side of the TKX. Very unlikely it's bad. The two wires from the TKX VSS are high signal and low signal. Typical for non-GPS speedos is green wire to the "IN" connection on the speedo and grey to ground. Hopefully that's the case for yours. Although I've often heard from others it doesn't matter. Just so one side is grounded. This has come up before and it usually solves the problem you're describing.

The mechanical VSS location on the LH side is typically not used unless you need a mechanical speedo cable - who does that any more - or some other unique reason. The transmission comes with that location covered and should stay that way in your case.

I too have some confusion on this, I have the dash harness speed sensor wires green hooked to gauge, grey grounded. Speed sensor plug on rear harness plugged into tkx trans supplied sensor as described. However there are two additional wires green and grey on the engine side bundle that I have no idea what to do with? I have the same setup as post author. I have no tested mine yet so who knows. I assume the additional wires are just capped not for use.

[edwardb]

I too have some confusion on this, I have the dash harness speed sensor wires green hooked to gauge, grey grounded. Speed sensor plug on rear harness plugged into tkx trans supplied sensor as described. However there are two additional wires green and grey on the engine side bundle that I have no idea what to do with? I have the same setup as post author. I have no tested mine yet so who knows. I assume the additional wires are just capped not for use.

There are two sets of speed sensor wires. Both from the same source. One in the dash harness and one in the sender harness. Just cap the sender ones if you don't need them.

[JohnnyDeere]

There are two sets of speed sensor wires. Both from the same source. One in the dash harness and one in the sender harness. Just cap the sender ones if you don't need them.

Thanks man!!

[PMD24]

I believe your speedo is electronic. If so, Rf harness plug plugs into PS of transmission. Wires then go to dash harness, and the green/grey wire stubs in the dash harness are green to speedo and grey to ground.

Pat

[Blitzboy54]

There are two wires from the sensor, green and grey. Up in the dash harness the green wire attached to the speed input of the speedo. They grey wire is grounded. Do you have the grey wire grounded?

This was my issue on my first build. I don't remember if the manual tells you to ground it or not. The other is the TKX uses a different connector than the RF harness. The RF harness comes with a connector for the foxbody T5.

You need one of these

https://www.amazon.com/dp/B01EEO84BY...d_asin_title_1

[Wizbangdoodle]

Mystery solved!

To all those that called out the gray wire to be grounded, you win a stuffed toy.

I came here to post my solution and lo and behold several of you have the answer. I went to a car show this morning and got a lot of compliments, but I kept thinking about this speedometer. I got home and looked at the RF schematic and then the Autometer speedo manual. From that a figured out that the gray wire, which is labeled "EFI Speedo Signal Return" needed to be grounded. Initially I ignored this wire, 1) because I don't have EFI and 2) because the manual did not mention connecting anywhere (at least that I remember). I put a temp alligator clip on it and it started moving as soon as I drove the car. That made me happy. I just got back from calibrating the speedo and all seem well. Thanks for the help everyone.