94 C280 check engine code (P0134: O2 Sensor); Regular gas (Octane 87) related?
 

Hi all,

Got the check engine light few days ago. Went to Autozone and borrowed a OBD2 scan tool, and the scanner says "P0134 O2 sensor CKT no activity (Bank 1 sensor 1)". Delete the code and the check engine light has NOT returned yet after 2 days (but only about 25 miles though). I use 89 Octane gas for about a year and started using 87 gas about 2 months ago when it gets cold in the winter. It did get a little bit warm (about 70F) last week and I was a little bit heavy footed. Do you think this problem is 87 Octane gas related? The car is 11 years old and has about 93K miles. The O2 sensors are still original. Thanks.

Octane has nothing to do with your O2 sensor.
If the light comes back on, you can either test the O2 yourself ( do a search here ), or have somebody with the right equipment & knowledge do it for you. ;)

Ok, it has been a week now and the check engine light has NOT come back. Is it just a false alarm or should I be worried about the O2 sensor?

Do not worry about it until ( if ) it does come back on.
Could have been a false alarm. CEL's have a habit of doing this sometimes.
I guess computers can have a bad day, just like some of us. ;)

It has been about 2 months and this problem comes back about 3 times already. The check engine light always comes up first thing in the morning (never during the day) when I turn on the engine. After reset the light with the OBDII scan tool borrowed from Autozone, it will stay off for 2 to 3 weeks. I don't mind keep resetting the light. But the only thing concerns me right now is that this car is due for a smog check. Do you think I should have the problem checked out before the smog check? Thanks for your thought.