I have been searching...what does the VSS acually do?

[LavaSurfer]

I just can't seem to find anything. What does the vehicle speed sensor acutally do? My cruise works fine, speedo works great....what else could this thing do or control? I have always gotten the CES light while slowing down from interstate speeds, but lately it has been coming on all the time once I get going....so I know its getting worse. I just don't see anything wrong but the stupid light coming on! :wtf:

[SteveDX89]

The VSS is for your speedo. It displays your speed obviously. However, there's also an electronic signal that goes from the gauge cluster to the ECU. This is to let the ECU know how fast the car is going. I'm sure it has to do with properly metering the fuel for the best combustion along with O2 sensor readings, etc.. When you have a check engine light, the ECU defaults into closed loop mode to protect the engine. It's probably dumping more fuel than usual into the engine now to keep it from running lean and detonating. How much more fuel, I don't know but you should look into the problem. The wire that runs from the cluster to ECU is tied up in the harness so you'll need a wiring diagram to figure out which one it is. I would look to see if maybe that wire is broken somewhere along the line. The best way to tell is to touch each end of the wire with an ohmmeter. If you have resistance, the wire is fully intact. If there's no resistance, there's a break somewhere.

[LavaSurfer]

I have been averaging 22-25 MPG with about 75% being interstate driving. When I bought this car I was thinking that I might get a little better, but I do drive this car pretty hard as I have never owned anything with less than 8 cylinders so she gets floored merging and passing on a regular basis.....so I guess I'm not complaining. Also when on the interstate I am always doing 80-90 (yes I speed a lot, i got it from my dad). I have gotten 26-27 once when I was doing a lot a cruise control while on a short trip. Is the mileage I am seeing about normal?

[LavaSurfer]

I just went to the junk yard and picked up a new cluster....so NO MORE LIGHT! This is amazing cause I have been putting up with it for more than a year now. So I will see if I get an improvment in mileage or not....I for sure and hoping I do.

[mgardner]

Ok, I've had the CEL come on a couple of times because of this too. I'm wondering if I should change the sensor (the one in the dash?) or is that the only one on the car? Or would I even be able to find a suitable replacement sensor?

Thanks.
-Mark