A common cause for that code would be a loose gas fill cap or a damaged/missing O ring seal on the cap.
It means your sensor heater in Sensor 1 or Bank 1 is malfunctioning. Get it replaced.
how to diagnostic this code
The diagnostic code should go off when the issue is fixed. You can try disconnecting the battery for a few minutes. Also, it can be reset through a code reader.
This is a powertrain code that signals an evaporation system monitor performance issue.
You need to reset the light by using diagnostic equipment even though the part was replaced the fault code will still be stored in the ECU memory.
The check engine light means that the computer has a problem code that you need to read. Use a diagnostic code reader for your vehicle. Your Chevrolet should be OBD2 compliant, meaning that you need an OBD2 code scanner.
What did the diagnostic code tell you before you replaced the EGR valve? You should not have replaced the EGR valve unless you have already run a diagnostic code otherwise you probably just wasted money. Oxygen sensors are a more common problem, especially since they routinely wear out. Also, map sensor, throttle position sensor, crankshaft position sensor... and a whole lot more, can cause a check engine light to come on. Don't guess; run a diagnostic code and figure out what the computer is detecting. Then replace ONLY what the computer indicates has failed.
Nasal endoscopy is a procedure, not a diagnosis, so it doesn't have a diagnostic code.
You can code Osteoarthritis as principal diagnosis
I have the same codes on my 2005 Explorer, According to what I'm reading elsewhere, the battery needs to be replaced.
Code 12 just means that the ECM is going into diagnostic mode, this is NOT a trouble code! Code 12 should blink a couple of times pause then blink your trouble codes if you have any. If you have no trouble codes, it will resume to blink code 12 again.
This code is for the transmission The Direct clutch speed sensor. Have it tested most likely it has to be replaced. Had the same problem myself and managed to fix it by replacing the sensor.