Hi, I am new to this post. thank you for the support!
I have 2004 honda civic LX 1.7 - history of the car is major overheating problem (on and off for about 2 years) / it was seen by 4 different mechanics and could not find the Issue. finally temp stayed on normal temp - head gasket replaced/ new water pump / new radiator / new hose / new temp sensors./ new thermostat.... after 2 months car looses power doesnt go over 50mph cannot go uphill it takes about 20 seconds to reach 20mph from a full stop. key light is blinking / temp is all the way down to C / check engine light is on / I took it to autozone to test batter and alternator it all passed the test. I plug by OBD2 reader cannot link to my computer. please help thank you!!!

P.S. I saw the belt for alternator is very loose but I already fixed that Issue but still no improvement!