VSS issue and trans 1st gear

[FAKKY]

Took truck around block.
All awesome from no leaks (new PS rack) and everyting working good.

Except speedo (VSS) and trans.


Whats the best way to test the VSS. I only have HP Tuners.


2007 LQ4/4l65e (rebuilt by me due to 4WD to 2WD shaft swap)
Digital Dakota

@ls1nova

[FAKKY]

lt1swap says ...

Pin 50 - Dk Green/White - VSS - This is a signal generated by the PCM, based on information it receives from the vehicle speed sensor located in the transmission. The PCM takes the sensor signal, and calculates the tire size, gear ratio programmed into it, and makes a 4000 pulse per mile signal. This is useful if you want to use a cruise control box. Some speedometers will use this as an input, others, like Autometer's, will hook directly to one wire of the speed sensor in the trans.


But this sounds more for the gauge itself ...... which it could be ....... but how to diagnose if VSS is getting a signal

[FAKKY]

C2 Green
20 LT GRN/BLK 822 VSS Low Signal
21 PPL/WHT 821 VSS High Signal


Now what do do with it

[ls1nova71]

Its Saturday night, some people have lives! Not me though apparently....
But anyway, what's the issue with the transmission? I assume it's not shifting and you don't have any speedometer movement?

[FAKKY]

Originally Posted by ls1nova71

Its Saturday night, some people have lives! Not me though apparently....
But anyway, what's the issue with the transmission? I assume it's not shifting and you don't have any speedometer movement?

Lol. NO life you - your skills are needed elsewhere.

Truck seems to not have 2nd+ gear I need to confirm tomorrow but didnt really feel a shift .... eg might disconnect harness and see if it feels any differnt (start in 3rd).

I have a guage issue and a trans shift issue. I am hoping they are one and the same Basically doesnt feel like its shifting out of first. No signal to the dakota digital gauge. All other gauges working. I know you can tap direct into the VSS signal wire ping #50 for certain gauges .....

Is there a way to see if the PCM is actually getting the signal from the transmission VSS ? eg Can you lift on jacks and put into gear and use HPT to see the command ?

Or a better/other way ?

[ls1nova71]

You can put the rear end on jackstands and put the truck in gear and watch the scanner in HP Tuners to see if its reading any MPH. If it isn't, then you would need to check the wiring on the two wires between the PCM and the VSS.

[FAKKY]

Originally Posted by ls1nova71

You can put the rear end on jackstands and put the truck in gear and watch the scanner in HP Tuners to see if its reading any MPH. If it isn't, then you would need to check the wiring on the two wires between the PCM and the VSS.

Awesome thanks man.... I'll report back tomorrow.

[FAKKY]

Well ..... dont have VSS ....... but looks like when I command the trans to shift via HPT it
shifts ---- at least 1-3 .... and I think 4 as well but harder to tell without load ��

Now to track down if its a wiring issue ...... or a sensor issue /other.

[ls1nova71]

If you can shift the trans with HP Tuners then I would say it's going to be fine. Pull the PCM connector off and unplug the VSS at the trans and do a continuity test on both wires, Look for backed out connectors in the plugs and also look to make sure a pin hasn't pushed in in the PCM its self, I've seen that happen before.

[FAKKY]

The green 20 LT GRN/BLK 822 VSS Low Signal has continuity with ingnition on - just grounding to frame to other side to wire at trans.

21 PPL/WHT 821 VSS High Signal has no continuity. Not sure if it should. (again - just grounding to frame to other side to wire at trans.)

The Sensor has 1.9k OHMS.


This was a 4WD to 2WD conversion .... the sensor is new.

[ls1nova71]

Not sure how you're doing your continuity test, but you shouldn't have the ignition on and you don't ground anything, that could potentially cause problems. Just unplug the PCM connector and the VSS connector and using a DVOM, put one probe on one end and the other on the other end. You should have continuity on both wires. Try moving the harness around while testing to see if you lose it or gain it, which could indicate a broken wire inside the harness.

[FAKKY]

OK.
What are the low and high used for ? Both used by PCM ?

[ls1nova71]

They're just the wires to the PCM from the speed sensor. High and low is basically power and ground, but it isn't like a 12v power or anything.

[FAKKY]

So this time I did normal continuity by unplugging the VSS and other side at PCM (C2 green and pin/probe 20 and then 21)

Ie just a direct wire continuity test
Both have continuity and are fine

[ls1nova71]

PCM pins looked good, no pins pushed in or anything? Aside from that, the only thing i can think of would maybe be a bad speed sensor, or maybe the reluctor on the output shaft isn't in the right place. Since you said you swapped the output shaft, it does have the reluctor on it, doesn't it?

[FAKKY]

[FAKKY]

Wish there was a way to put a temp gear that matched in a drill or something and spin her up close to connected sensor and see the signal move .... (or not)...

[FAKKY]

I'll try reseating everything ....... see what happens

[FAKKY]

No difference

[FAKKY]

If I run down and grab a new VSS sensor ...... given it was a 2007 4WD to 2WD ... differnt housing

What sensor ....... same ?

[ls1nova71]

I would tell them you need a sensor for a 2wd, not sure there is a difference though. What brand was the one you bought? Some aftermarket sensors are just junk.

[FAKKY]

Well ..... effit ........ it was the sensor. Replaced with (another) new one ...... all good.

Thanks NOVA !!! Im gonna PM you.

[LS short box]

Same thing happened to me. Brand every thing in the trans and the VSS sensor was junk brand new. Glad you figured it out.

[FAKKY]

Originally Posted by LS short box

Same thing happened to me. Brand every thing in the trans and the VSS sensor was junk brand new. Glad you figured it out.

I was sure it wasn't that (being new). So even at end I was hesitant to drop $25 on something I thought wasnt broke.
Well what do you know ......

She runs so much better now ...... I need to adjust the tire size and maybe gear ratio and get the gauge cluster working ....... but asides a few tweeks here and there - fun !!

thx all