2002 Chevrolet Blazer LS 4dr 4wd 4.3L
 

Please Help Me. I cannot figure this one out.

I am trying to pass the yearly emissions and inspections in PA. This year I had a SES & ABS light on, for misfires in cylinders 1-4, right wheel speed sensor, and O2 sensor. I replaced both wheel bearings, the O2 sensor, and all 6 spark plugs, spark plug wires, distributor cap and rotor. Both SES and ABS lights were off and the engine was runnig very smooth and strong. The morning I left the house for my emissions test while driving to the shop, SES came back on and the Engine Temp gauge dropped to Zero. I replaced the thermostat when I purchased the blazer on 11/19/2020 with 113,450mi. It Currently has 118, 200 aprrox. So having read other threads I replaced the Temp Sensor today. That did not fix the issue. I checked all the fuses, none were blown. What else could it possibly be? and ECM issue? Thanks