My car is a 2004 Civic dx M/T with 115k miles. Three days ago I noticed my CEL came on and I pulled p0134 - no circuit activity on upstream O2 filter. Figuring it was probably time for a new sensor I ordered the Denso one off Amazon ($98).

Anyway I cleared the code and now it's not coming back. I'll have a shiny new sensor on my porch this afternoon and I'm wondering if I ordered with too much haste. Should I slap it on? Hold on to it? Or send it back and save the $100 for a rainy day?

I've had the car for two months - it runs great. My mpg seems slightly low though: 27mpg with pretty light-on-the-pedal town driving. What do you think?

 

Update: Spent the morning learning how to use the $7 multimeter I bought.

I checked the harness and have have 12 volts of power coming to the sensor and heating element and the grounds look good. Is there any way to test the actual sensor without pulling it out and heating it up like I've seen people do?