I got in a little fender bender yesterday, and it messed up the driver side front corner of my car. :-(
After this happened, i noticed my check engine light came on. My car still seems to drive fine, I notice no difference in its driving ability. I self-diagnosed my engine light and it told me i needed a "knock sensor" and a "rear-heated O2 Sensor." What are these? Is this a critical thing that I should get done immediately? Where can I get them (besides the Nissan dealership)? and how much do they cost? Please, someone help! Thanks
- David

 

The rear O2 sensor monitors the exhaust gas mixture. The knock sensor senses knock in the engine from detonation. This can occur when the octane level in the fuel is too low. If you don't already put premium gas in your car every time, start doing it. You will get better gas mileage and slightly more power....and no knock. Your gas mileage will probably decrease from the bad O2. I had both of those codes and I replaced only the rear heated O2 sensor. CE light went off and never came back on again. No codes are present, and my gas mileage is 22-25mpg city, over 30 hwy. Many people say that a bad O2 sensor also robs your car of a lot of power.

 

I havent noticed any difference in my car's performance, but how much does an rear heated O2 sensor cost?

 

I think it was like $80. I also got a discounted price on it because I work at a car dealership.

 

80 dollars is too much, go to www.oxygensensors.com...65 SHIPPED

 

Go to www.thepartsbin.com and get the OE Bosch for $66-67 shipped. Or if you want Denso or NTK O2 sensors you can go to www.sparkplugs.com and input the part #'s found at the company website. i just replaced my 02 sensors and knock sensors.
Good Luck.

 

You won't notice any difference in MPG or performance with a dead rear O2 sensor. Only the front ones are used to regulate the fuel injector pulse width and the air/fuel ratio. I would say reset the CEL and see what comes back.

You would see a nice improvement in performance if you replace a defective knock sensor, so if you can only do one at a time, leave the O2 for last.

 

I'd be concerned about that.
Why would a front-end fender bender mess up the o2 and knock sensor?