check engine light stays on after repair
 

New thermostat (oem) ACDelco 131-158 installed
after a while......
coolant guage flattens - digital coolant guage goes blank, ac goes off
I erase code, p0128,
guauge comes back on, ac starts
After a while Check Engine Light back on
again
coolant guage flattens - digital coolant guage goes blank, ac goes off
clear code, guage back on, ac on

Then the temp sensor is bad.

air in system?

X2^^^^^, you need to burp the system first, then if still getting the code , change the coolant sensor.