98 4L 210km.
Check engine light came on the other day, and a friend suggested putting in some supreme fuel. Sure enough 10 minutes later the light went off. What with that? Oxygen sensor?
I'm going to pick up an obdii code reader, but is there any sequence of buttons I can press to get a readout in this vehicle?

 

More than likely, if the lite comes on and goes off after a bit, it is the O2 sensor starting to go out. Putting different fuel in it probably didn't really affect it, the sensor started cylcing again and that turned the lite off.

 

Thanks for the reply. I will replace sensor soon.

 

You need to have the code read because there are two upstream and two downstream sensors. It is probably one of the two upstream ones. Those are the ones closest to the engine.