Yellow "Check Engine Light"
 

Gentlemen,
I have recently changed the conventional oil to the synthetic Sae 5W20 and went 180 miles to the PA mountain resort... On the way there: "Check Engine Light" (yellow) appeared... Light Appeared on the highway, during the 65-75 mph speed (on the cruse control). No temperature rise have been noticed, no special sounds or smells... Please help me to figure out: "What could it be?"
Your kind attention to this matter is greatly appreciated!!!

You need to get the computer scanned for the code.

It could be the O2 sensor. The sensor measures the fuel injected and the excess remaining and helps to regulate fuel usage. If that is the code you receive, it is safe to drive the vehicle but gas mileage could be effected. (1-2 mpg)

O2 sensor
 

Dear, Sir.
Thanks for your kind support. Please kindly let me know: "Where is this sensor located?" or if such thing possible - please kindly post the picture (photo of the item) Thanks.

There are 2. One before the cat and one after. Which one needs replacing? You will only know that by having the computer scanned for the code. Don't just 'throw parts' at the problem. Diagnose correctly before spending money on parts you don't know are bad or not.

many auto parts stores will run a free scan for you

O2 sensor
 

Thanks much for your kind support!

O2 sensor.
 

Thanks for advice.