Originally Posted by 03CanRunner

Sorry for the long write up, I'm a technical trainer I spew out way too much detail,... I know....
I had this issue too. from your message you do not have a CEL( Check Engine Light) which is on. That could be key here. Also you do not list what year your 4runner is?

For the 2003 to some of the 2005 model years there appears to be an issue when an ODBII scanner is hooked to the 4runner to get codes. Sometimes if a car is serviced for a reason other than one that shows a CEL on the dash the mechanic might still hook up the ODB scanner just to check if he can see any codes, or past codes....

So did you get you truck serviced recently? If this is the case, then the problem with this model year (2003-2005) is that sometimes the ODBII scanner erases the information needed for the truck to perform VSC.( but not always, so it is funky)

This situation should not prevent ABS from working. These are separate systems. If there was an ABS problem the ABS light would light up too. To reset the VSC, you need to perfrom a Zero Point Calibration. The TSB (Toyota Service Bulletin) BR 001-04 shows how you can do this, using another ODBII scanner or one from toyota, or there is also a manual way if you want to save a few dollars. I did this at the dealer with their scanner and it cost me some 64$. You can google for this TSB 001-04 pdf.

The other reason that this can occur is if a new key is coded at the dealer for your truck. I had both of these situations on my 4runner (2003 model) and reset it at the dealer. Other situations might cause this to happen too, maybe a dead battery??

The Zero Point Calibration basically tells the VSC system when the wheels are turning and when they are not not. So the calibration basically sets the truck back to zero point. So that VSC can do it's thing and maintain stability when it notices that the wheels are not spinning at a similar rate, slipping, skidding etc....

It is key for the above that you do not have a CEL or the ABS light on too. If you do, bring it in for service or at least bring it somewhere that will read the codes for you. Once you have the codes you can post them back up and or research what the code means. For the CEL sometimes it can be as silly and simple as a believe it or not a gas cap that is not tighten properly.

Many codes will cause the VSC and VSC trac to light up. This is not tied to ABS. Try it, on a slippery surface. You will be able to feel the abs kick in when you hit the brakes real hard to verify if the ABS still works. The 4runner turns VSC off under tons of conditions to prevent engine damage. Since the 4runner can use engine braking and cut the power when VSC kicks it. So stopping VSC will prevent the engine being used in this way, thereby helping to prevent damage.

Check out the BR 001-04, it will show you how to fix it with toyota or manually. Write back to tell us how things are progressing. maybe we can continue to help.
J