02 Nissan Sentra Not Shifting

I live in the Midwest. This problem is really hard to describe. About a month ago, during super-cold weather (teens or single digits) while driving in traffic I felt the transmission sort of ripple or slip as I slowed down for a red light. When I attempted to go forward on the green light, the car resisted at about 10 mph - kind of like trying to go 50 mph in first gear - like it wasn’t shifting. At the repair shop they told me there was ice around the wheels and they chipped it off. They drove the car and said it didn’t have the other problem. A couple of weeks later, the car did it again, this time near a shopping mall, also on a very cold day (teens or 20s). I drove it into the mall at around 10 mph, parked it, was in the mall for a while, came out - no problem until last weekend - also very cold weather (teens or 20s). This time it happened at around 40 mph. It started to slow down and I could feel the transmission slipping or rippling, then it felt like trying to go 50 mph in 1st gear and abruptly slowed down to about 10 mph. I pulled over to the side of the road, turned the ignition off, waited about a minute, started it up again and it was OK. No more problem. I took it to the repair shop and told them what happened. The mechanic said it’s not the transmission because they checked it when they had it before. He said it might be the part of the computer that tells the transmission at what speed to shift. They now have the car, have driven it about 20 miles, the problem didn’t show up, and one of the mechanics took it home to drive around over the weekend. By the way, the Service Engine Soon light has been on for about 2 years. I took it in once to have it fixed and it stayed off for a few months, then came on again. It’s been on ever since. I read in one of the discussions about getting a code read at Advance Auto Parts, but I don’t know if that would help. Thanks for your help.

" the Service Engine Soon light has been on for about 2 years…it stayed off for a few months, then came on again. It’s been on ever since."

No responsible mechanic (or most of us in this forum) would attempt to diagnose a problem w/o first retrieving the stored trouble codes (after 2 years, there could be many of them), so you really need to get those codes, and then come back to this thread to post them. They will be in a format similar to “P0123”.

When you come back to post the codes, we will also need to know (in detail) about the car’s maintenance–at least over the past 3 years–and we will need to know the current odometer mileage as well as a description of your driving patterns (solely local driving, mostly highway driving, or a mix of the two)

And, in the meantime, I have to wonder if anyone has bothered to check the transmission fluid.

“the Service Engine Soon light has been on for about 2 years. I took it in once to have it fixed”

To VDCdriver’s comment, I would just add a couple of things. One is that the light itself is just a bulb in the dash on a circuit. It the light is on, there isn’t an “it” about it to be fixed. What it indicates is any one of a very large number of possible problems.

Second, your problem is intermittent and this can be very difficult to sort out. It sounds like an intermittent problem is putting the transmission in “limp mode.” Sometimes you have to have it scanned while it is acting up to “catch” the right code.