Nissan Repair: check engine light, nissan sentra, gas cap

Question
Hello,
I bought a '98 nissan sentra gxe (automatic) 2 months ago. 2 days after i bought the car the check engine light went on. I took it to my mechanic (but unfortunately i dont remember the code) and he told me that there was a kind of pressure drop at the front of the car. He reset it and light went off. After that i used the car about 500 miles but yesterday when i just entered a highway and started to accelarate(around 50 miles) the light went on again. I usually drive the car to school and don't speed up too much because i live in a small town :) Well anyway my father realized that, sometimes there is no " fisss" sound coming after untightening the gas cap. But not always. If the problem is still the same as the former one which doesnt sound as a major problem to me, is there any problem if I keep driving the car? Thanks in advance!
Jade

Answer
Jade,

If the pressure cap is not holding the check engine light will come on.  It will also come on if the cap is not tight.  If this is the case there is no problem.  You could go to Autozone or Checker and get the code checked for free.  If the cap is the problem they will turn it off when you correct the problem.