I have a 2003 4runner and after a strut change I felt it was loosing power so I asked for a full engine diagnostic. the diagnostic was Broken Oxigen sensor. this morning after starting a rain the check and the VSC Trac/VSC off was lights came on and never turned off since. Is there any reason for that>

Power steering rack an pinon is bad ! Have it check at repair shop

run the fault codes and check for transmission control, servo, solenoid problems

I would check to see if there's anything loose back in the rear and area of your suspension but it definitely could be a badd Strut

It sounds like the CV joints are going bad on the passenger side drive shaft. Make sure none of the obvious like ball joints, struts, springs, and any other suspension parts aren't loose or broken. More than likely its the CV joints, but if you do one side, might as well do the other. (an ounce of prevention saves a major headache later)

Take the upper strut mounts loose, take the lower strut mounts loose. Depending on what kind of vehicle we are talking about, you may need to disconnect a lower ball joint, a brake hose from the strut, or stabilizer links from the strut assembly. It usually results in a better answer if you take the time to mention YEAR, MAKE, MODEL, ENGINE SIZE, when you are asking for help with your vehicle.

Automobiles: 2006-2007 Ford Five Hundred 2WD & AWD, Montego

If the steering is getting a little hard to turn at low speeds, this would indicate a loss of Power Steering, and the steering is reverting to "Non-Power" steering, just like the days of the Ford Model T or Model A. Loss of power steering is usually caused by low level of PSF (Power Steering Fluid).
So first on my checklist would be checking the PSF level in the reservoir.
Also bleed (air) from PS (Power Steering) pump.

The Ford Five Hundred has front MacPherson struts, so check these for leakage (of the dampening fluid in the strut cylinder), or breakage of their coil springs.
These springs can actually weaken over time, but this is impossible to see - you must "feel" it by bouncing the strut up & down - preferably with your hands on the top of the strut tower in the engine compartment (rather than on the exterior finish).
If the MacPherson struts have weak/broken springs, these components are not separately serviceable, and the strut would have to be replaced as a unit (and preferably both left/right to maintain smooth/even ride).

The Five Hundred also has rear shock absorbers with springs - check for leaks/breakage/weakness here too.

Steering losing responsiveness/wander - checklist
Priority Action Part Type Cause
1 Inspect Rack & Pinion - Center Wear From Internal Fluid Leaking Around The Rack Piston.
2 Inspect Steering Stabilizer Bracket - Loose or Broken Steering Stabilizer Bracket.
3 Inspect Front Lower Control Arm - Front Lower Control Arm loose/missing bolt(s)
4 Inspect Front Lower Ball Joints - Front Lower Ball Joint(s) Worn/Loose
5 Inspect Front Upper Ball Joints -Front Upper Ball Joint(s) Worn/Loose
6 Inspect Tire Pressure - Tire Pressure should be 35 PSI for the Five Hundred and Montego's P225/55R18 OEM (Original Equipment Manufacturer) tires.

Harsh ride - checklist

1 Inspect Rear Shock/Strut - Shocks/Strut failing/leaking.
2 Inspect Front Shock/Strut - Shocks/Strut failing/leaking.
3 Inspect Coil Spring - Incorrect Coil Spring Selection or Installation.
4 Inspect Coil Spring - Coil Spring broken.

The engine vibration could be due to the following reasons:
1. Dynamic unbalance of any rotary part like bent shaft, misaligned engine pulley or worn out serpentine belt.
2. Defective, broken or stretched engine mounts.
3. Muffler or silencer pipe is touching the body from under the car.
4. Loose or missing nuts or bolts in the engine bay area (like loose compressor or alternator bolts).
5. Maladjusted bonnet.
6. Front bumper loose nuts and bolts.
7. Dynamic unbalance of the flywheel.

you need to check both of the control arm bushings,ball joints,sway bar links and upper strut mounts if all check out ok change the struts

You just answered you own question, get it diagnosed.

try by unplugin the oxigen sensors, specially if this car has been in an mufler shop for catalitics or mufler repairs, sometimes they are not to carrefull and might damage an oxigen sensor, this sensor are located on the mufler pipe, and they look similr to an spark plug.