VSS buffer pinout.

[Six_Shooter]

Well it seems that the VSS decided to die on my car recently, and I'm trying to diagnose what the actual problem is.

The VSS I used has a green box, that I believe is from an S10, probably between 1989 and 1992.

It looks a lot like this:
http://chevythunder.com/VSS_optical_buffer.jpg

I don't have a spare one of this type, I do however, have two with yellow boxes, that from my Google searching seem to be from something earlier, perhaps a 1985 F-body, or similar.

They look like this:
http://i270.photobucket.com/albums/jj120/apollols/CIMG3053.jpg?t=1295320314

Unfortunately I can't find the pinout for the yellow boxed VSS, and the connectors are different, so I can't just plug one in place of the other, which was my original plan.

Does anyone have a cluster with one of these still attached and can check the pinout, or know the pinout offhand?

[RobertISaar]

if you can come up with guesses as to which application might have the right diagrams, i can do some alldata digging.

[Six_Shooter]

Well, the picture of the yellow VSS is attached to a 1985 Camaro cluster, according to the thread I pulled it from.

[RobertISaar]

http://imgur.com/VDdoWWE,RbnFfKf

[Six_Shooter]

The second one is correct for this type of VSS, but still doesn't give pin out, just wire colours, of which there are no wire colours as you can see from the cluster photo above.

Anyway I figured it out with some inspection of the circuit and comparing to the old VSS.

On the green boxed VSS, there are 4 pins, one all by itself way away from the other 3 that I believe is to feed cruise control.
Then there are 3 pins near each other, one on it's own leg, and two on a common leg. The one by itself is the signal to the ECM, the middle pin is ground, and the other is 12V

On the yellow box VSS the pin out is essentially reversed. There are only 3 pins. The 12V pin is the one by itself, then ground is in the middle and then signal is on the same leg as the ground.

I now have a working VSS again.

The yellow box VSS seems more, well sensitive, not the right word, but I noticed that the speed indication happens quicker than the old VSS, but jumps around more at lower speeds. And this makes sense since the circuitry seems to just take the pulse from the emitter/detector pair and triggers a transistor to create the output. The green box VSS has what looks to be more of a buffer circuit, that will average sample pulses before creating an output. I'd have to find a data sheet on the IC used in the green box VSS to know for sure though.