Hello all. I recently purchased a 2001 Pathfinder LE with under 50K Miles and, after not reading the owner's manual, was unaware that it required Premium Gas. After a month of using 89 octane gas, the check engine light came on. I have since switched to 93 octane, but the light remains on. The Pathfinder has a super clean service record, which I obtained from the dealer. The engine sounds good(no knocks), and have not noticed any degredation in performance. A couple questions for you all:

1. Would using 89 octane gas even cause the light to come on?
2. If that is the cause, how can I get the light to shut off?
3. What else could be causing the issue?

Also, would using 89 octane gas cause my gas milage to drop?

Your assistance is greatly appreciated!

Josh

 

It sounds as if an O2 sensor has gone bad. Very common problem on thosa model PFs. Your model should have 4 O2 sensors. 2 upstream and 2 downstream. Whether or not yours is a CA emissions version is important as well. They go bad because of different gas formulations in different parts of the country at different times of the year. And yes you can get worse gas mileage if you loose an O2 sensor.