The check engine is on. Went to autozone, and a code came up for the 1-2 shift solenoid. The car drives great. The only thing is that I only feel it shift only once at 10 mph, and after that it doesn't do it anymore.I guess it revs or something. Idk I just drive it. Could you help me in the diagnosis of the problem? How much does it cost to fix? What do I need to do?