I have a 2000 Hyundai Sonata with 110K miles. It runs well, still quiet, good gas mileage. The problem is that it will not shift from 3rd to 4th gear. This is not constant. When I start it up cold in the morning, it shifts fine. But sometime during the day, when it needs to go from 3rd to 4th (often on the interstate), it refuses to shift. It stays in 3rd, the engine light comes on, and I’ll drive about 60 mph and try to keep the RPMs under 3000. It always “fixes” itself when I turn off the ignition. This makes me think the problem is at least partially electrical. A couple more things: it only happens when the car is warmed up – never when I drive it cold. Also, sometimes this will happen in 1st gear, where it won’t shift into 2nd, but jumps straight to 3rd rather violently. It’s gotten to the point where I don’t want anyone else in the family driving it because it is such a pain, and could possibly be dangerous. Any ideas?
I am not that familiar with Hyundai transmissions and the computer programing they use but it sounds like the transmission is going into ‘limp home’ mode. The fact that the ‘engine light’ is coming on indicates that the Power Control Module is seeing a problem and will most likely have set a Diagnostic Trouble Code. If you get the PCM scanned for codes by a capable scanner, the difficulty can be narrowed down. You may need to go to a transmission specialist or the dealer’s service department. Check with them ahead of time to make sure the shop can diagnose and has the correct scanner for your Sonata.
Good luck on this.
Sounds reasonable. I will have it diagnosed. Thank you!