2001 LS Traction control/Brakes issue

My son was driving car on the highway and the brakes were starting to apply and the engine lost power. Now the brake pedal stays very soft, Hardly
any braking power and the engine runs rough. Check engine light is on
and the Advancetrac control light is on. Any ideas!! Cheap fixs!!

Welcome to the forum!

Are you sure the brakes were applying? I suspect instead that your son is experiencing the dreaded leaking valve cover plug well seals, causing an engine misfire. Oil leaks from the plug well seals and starts to fill the plug wells. There is one ignition coil per cylinder, and the coil sits right on the plug (Coil on Plug -- CoP). The oil creates a path to ground for the spark, which causes a misfire. The misfire causes the engine to run rough, and since the brakes are vacuum assist, the rough running engine means decreased power brake assist. This misfire could be the cause of the Check Engine Light (CEL).

As for the Advancetrac light being on, that could be due to a faulty wheel speed sensor, or other issue. Did both the AdvanceTrack light and CEL come on at the same time?

You'll probably need to find someone with a professional scan tool to pull the codes for the AdvanceTrac system.

-Rod

Pretty sure brakes were applied. right front and left rear were hot
other 2 were cool. Brake pedal goes to the floor, very soft. when engine is
off the pedal is much firmer. I tried to bleed the cool sets but got very little fluid to purge out. reservor is full. when brakes were applied I could
still rotate the tire with some effort with lug wrench on a lugnut. And engine is still running kinda rough.

Swing by a local auto parts store and see if they offer a service to read diagnostic codes for no charge. Most do. Get the codes (by number, not just a description) and post them on this forum. At a minimum, that should give you direction on the rough running engine. If you're not comfortable driving the car, see if they will rent the code reader to you. Usually they will want a collateral amount for loaning you the tool, and when you return the tool undamaged, you will get the full amount back.

Most auto parts stores do not have the tools to read the AdvanceTrac codes, but maybe in the process of fixing the engine issues, your AdvanceTrac and brake issues may get remedied in the process.

-Rod

OK hit Auto Zone today got codes po136 & po306.
mis fire on 6 and oxy sensor. They could not read the brake system codes.
Today was the first time I looked under the hood of his car. Where are the spark plugs?
are they way down low or under the large what looks like a valve cover?

The spark plugs and coils are under the caps on the valve covers. The car uses a "Coil on Plug (CoP)" configuration. There are no spark plug wires, the coils sit directly on the spark plug. There have been numerous problems in the 2000-2001 (and somewhat into 2002) with leaky valve cover gasket spark plug well seals causing misfires.

Does your son's LS have the V-6 or the V-8? I think plugs on the V-8 are actually easier than on the V-6.

-Rod

This has the V-8

can anybody tell me a location for a relay or fuse to disable the traction control.

The stability control is all integrated into the ABS module, so to disable the stability control, you'd also disable the AdvanceTrac. I wouldn't recommend this.

And, yes, the Auxilliary Junction Box is under the hood and the Central Junction Box is inside the car, under the dash panel.

-Rod