what does the vss controll

Not sure about the stock chip but with aftermarket chips the VSS is neccessary to facilitate features like lean cruise, boost scaling, studder, and fueling based on MPH..

TurboDave can probably elaborate on this topic.

powersix

The VSS is only a PM generator that sends a converted signal to the ECM to determine vehicle speed. The ECM uses the info for multiple functions.

Pretty much covered by Orlando! In aftermarket chips (depending on brand) it is used for many things!!!

In the stock chip it's used to determine TCC lockup points, and one other function I can't remember, being here at work and unable to look at my "stuff". wink

so if the speedo doesn't work and you have an aftermarket chip would the car run real bad?

demonturbo:
so if the speedo doesn't work and you have an aftermarket chip would the car run real bad?

Click to expand...

Probably not, just some functions wouldn't work. The most obvious being no TCC lockup. And no closed loop idle if your chip is so equiped, which could make for a rough idle on a badly tuned car (that the chip may have been masking).