The first time my check engine light came on, I brought it to the dealer, and I got it repair (it was the O2 sensor)it's like a week ago. And now, the light is on again!! so I decided to check what's wrong by myself with the "ECU fault code diagnosis" in the FAQ section and I got the code 0707 and it means "rear heated O2 sensor". Last week when I brought the car to the dealer, they replace an O2 sensor so I was wondering how many O2 sensors are there in the car? Is it the same O2 sensor that isn't working or can it be another one? Please I need help!

 

Rear 02 Sensor has no physical affect on performance.. it only monitors the cat.. just reset it and go again.. if it comes on again.. replace it if you like.. but its really no big deal

 

yeah but I want to know how many O2 sensors there are on the car cause if it's the same as the one they changed, I'm gonna go there and complain and get them to repair it again! It cost me 200$ cnd for this little **** and I want it to work right.

 

umm 2 in the y pipe, 1 behind the cat....another configuration is 2 in the y pipe 1 in the cat...there could be more...

 

So it's maybe not the same that they changed last week...
If I dont get it repaired, will the car consume more gas?

 

like i said before homey.. it doesn't affect the performance of the car.. only the front 02 sensors do

 

I believe there are (3) O2 sensors. At least on 4th Gens.

2 on the Ypipe and 1 right after the cat convertor.

Here's the pic they have at Courtesy Nissan:

 

thats what i dun said

but pictures are good

 

Sometimes a piece of grit can become lodged on the sensor. It won't like this and will set off the CEL. Since they were just workin on it, they probably loosened somethin up and now it got lodged on there. Give it some time to clean up.