Flushed my transmission fluid and immediately felt the the car idle better and run smoother. 2 days later my dashboard has a wrench 🔧 light come on and the manual doesn't explain reason why. A day later my car will not exceed 80 mph, then 70, and then I can't go above 55. At the next light my car doesn't excelerate above 35 and then gives out; not even reverse works. Could I have damaged something by not flushing it properly or just a bad coincidence for a problem that I couldn't avoid?

 

To answer your question, yes something could have been disturbed. The PCM has detected some sort of fault and a code scan would be a good place to start.