How do u check for ecu codes

How do you check for ecu cdes without having to run a diagnostic.Ive got a 98 Max and my engine light has turned on recently,she is really sucking back the fuel, i figure its the o2 but i want to be sure,is there a way i can check without going to a dealer.Thanks .p.s how do you reset the ecu.

http://vbxmaxima.8m.com/ecu.html
Looks like you've done some work to your max looks cool. Thank you for posting this info. My CEL has been on for about a month or so but it still
drives and sounds good and gas milage is good.

This is perfect to check what the problem is.

Thanks that was really good info.

thanks, and good luck with the maximas