First of all, I am a total novice in engine electronics, trying to learn as I go.

I started getting codes 0304 and 0707(KS and rear o2) occasionally a few weeks ago. Each time the CEL came on I just checked the codes and reset it.

I know the KS code is a ghost.


Lately though, things are different and I am getting 0304 and 0303 instead of 0707. So now it's the FRONT-left o2 instead.


Why did the rear o2 stop setting a code? And why did the front-left just start?

Should I really replace the front-left o2 when it may just 'fix itself' like the rear did?

Normal behavior has been for the CEL to come on once or twice a week, and seemingly more likely after driving harder than usual.

 

How many miles does your car have on the odometer and how long have you owned it?

Is your car a Federal or California version?

It looks like you might need to consider a set of new O2 sensors.

Whenever I buy a used 4th gen usually with mileage over 120,000, I refresh the O2 sensors with a set of new NTK. That keeps away any O2 sensor codes for many years to come.

 

You might want to clean the contacts of the oxy sensor fuse. Its located on the right side of the fuse panel by your left knee.

 

Agreed ...

This is one of those maintenance issues that should be addressed regularly and at the recommended intervals at a minimum.