Why do simple malfunctions disable VSC/TRAC?

[BigBoss]

I own a 2005 4Runner V8 (rear wheel drive). I recently had some emission problems with my cats/o2 sensors which tripped the CEL. What I don't get is why a small problem like this disables an important safety feature like VSC/TRAC and AUTOLSD. I am stationed in northern Italy which means lots of rain and lots of round-abouts. Some of them require a pretty sharp turn and when you add that with rain, a V8, and rear wheel drive you can imagine there's a lot of slipping and sliding going on. I eventually got the CEL to go away (put a simulator on the oxygen sensors since there aren't any emission laws in Italy). Does Toyota do this to immediately force average drivers to take their vehicle to the stealership? I'm just ranting, any thoughts?

 

[TRDCal]

I could be talking out of my arse here but this is my theory...

VSC uses engine throttle to do it's job so when the computer see there's a problem with the engine (ie CEL) it disables the VSC just in case. I don't think the truck knows what the CEL is, even if it's something silly like an emission code, the computer just assumes the worst. On that note, I'm not sure why it also disables trac and auto LSD, but I assume it's cuz the systems are all somewhat tied together.

That's my thoughts anyways, maybe someone else can chime with a better theory.

 

[SR5 Iron]

Perhaps it makes it more of a reason for you to take it in for spendy service.

 

[ClockWork]

Driver slower to prevent sliding. Most Americans don't regularly service their car - even when the CEL is on. Lighting up safety features makes them take it to the dealer.

 

[BigBoss]

Today my CEL lit up because my gas cap was loose. Not a big deal except that also disabled the traction control. I wouldn't mind all these CEL if all they did was sit there. Why they disable the traction control is beyond me.