The 'check engine" light on the dash comes on about once a week for a duration of a day or so. Is there any simple inexpensive test equipment a D.I.Y. can buy to diagnose or troubleshoot the problem.

I understand the “check engine” light monitors at least one hundred functions.

Someone said that it maybe an O2 sensor. There are four on the car.

Thanking you, in advance, for your assistance.

mike