Buick Century Dealer Problem

Hello!!!!!!!!!

This web site is Fantastic ( and I did make a donation)

I bought a 2002 Buick Century Custom 4 door 3.1 L V-6 engine with 77,500 miles on 10-02-07. Two days later the check engine light came on. When I took it to Autzone they got the following codes... P0717 and P0716.

I have a 90 day 3000 mile limited warranty. I believe it is known in the business as a "powertrain warranty".

The place that I bought the car from has asked me to bring it in on Monday 10-08-07 so they can diagnose the problem.

The check engine light stays on for about 12-24 hours and then goes out again.

It seems to take about 2 "drive cycles" to get the light to come on again. Although this has not always been successful.


Questions

1) if the the problem is a speed sensor... I think I've heard that this is a costly repair and that I might as well have a new transmission put on...

Is this correct?

2) I'm concerned that if this is a costly repair that the dealership won't honor the warranty or they won't even acknowledge that they (may) have sold me a lemon car... (for eample, they might say, we don't replace sensors that are in the transmission, we only replace parts like the flex plate fly wheel etc.......so what do I do...

I don't have much money so if the dealership won't help....and the problem does turn out to be a speed sensor...
would you recommend a)replacing the sensor, b)getting a new transmission or c)just driving the car until it breaks and hope that by that time I have a nice down payment for a "newer" used car.

3) If the check engine light goes out overnight, will the mechanics still be able to diagnose the problem... in other words does the computer store codes and if so how long does the computer store codes?

4) I came across something called the "General Motors (specific) OBD II Drive Cycle". The web site is http://www.lyberty.com/car/drive-cycle.html.

The reason I mention this is... this is exactly what I was "accidently" doing on the day this first started. Right down to letting the car idle with the air condition and the rear defroster on at the same time....even the driving pattern is almost the same things I have to do when getting to work.

Could I have "accidently" set off a false code by doing this?

Thanks in advance for your help!!!!!!!!!!!!!!

Brenda


UPDATE***************************

I took the car to the dealership that I bought it from this morning (10-08-07, Monday). I bought it from a Toyota dealership... anyway, the service department stated that there was no code stored in the computer. The last time the light came on was 10-05-07 Friday about 8 pm. I have not been able to get the service engine light to reappear since then.

5) Should i take it to a Buick dealership for a second opinion?

6) Don't codes stay stored in the computer for awile?