I have an 01 jetta vr6 the check engine light came on and the code that comes up says that it has a problem with the transmission speed senor and the oxygen sensor, as soon as the light came n the car shifts later than it normlly would this problem is off nd on when the light goes off the car shifts fine I hav already changed the speed sensor 3 times and it still does the smae thng a mechanic told me that the oxygen sensor could also be causeing these problems because the car is nott getting the correct air and fuel mixture and it's throwing the timing nd everythin off is this true?