Service Engine Soon Light - For What It's Worth
My SES light has been on for several months. I didn't worry too much earlier this summer when it started to come on and stay on. However, as October approached (the month my '01 Frontier gets inspected), I started to worry. No inspection stations will inspect the vehicle if the SES light is on.
I read all of the information on this site related to the codes wrt the SES light. I went to Autozone and he determined that the code was "P0420" which relates to plugs, injectors, O2 sensor and catalytic convertor. I was going to spend some money on the small parts first. However, before I bought the parts, we had a cool front blow in to the Houston region during the day while I was at work. Believe it or not, when I started my engine, the SES light did NOT come on. I drove home (30 miles, 45 minutes) and the light never came on.
The next day I went to have my Frontier inspected. The light was still off. It passed. Later during the day, the outside ambient temperature started to rise. The SES light came back on! Is this a temperature-related phenomenon?
The truck passed inspection, so I'm happy.
One fix that the Autozone rep gave me was to disconnect the battery for a few minutes. This resets the engine computer and will turn off the light.