I just downloaded the info that was causing my service engine soon light to come on:

0302 - EGR problem
0303 - O2 Sensor problem
0304 - Knock Sensor problem

Any chance that these may be related to one cause?

My minimalist solution would be as follows:

0302 - Fix if I cannot pass the state emission test (TN)
0303 - Do not replace - Accept lower performance and worse gas mileage
0304 - Do not replace - Stop buying 87 and start buying 93

The car has 130,000 miles and is driven less that 8,000 per year.
Comments/suggestions? Thanks.

Craig

 

sometimes the knock sensor code will go away if you take care of the other ones first, so i would wait till last to try to fix that code.

 

If the EGR isn't working you will run a bit on the rich side. That could throw the O2 readings a little off and cause a fault code. The KS code almost always comes along with any emissions related codes. I highly doubt it's bad.

Fix the EGR system and clear the error codes. Drive the car for a week and check for any stored codes again. If you get a CEL with the O2 code followed by the KS code, replace the O2, clear the error codes and drive it around again for another week or so. Then check for any stored error codes. If the Ks doesn't reappear your good to go.

The grade of fuel you use does not have any effect on the KS sensor.

 

TN doesn't have state emissions. That's why you see those rust-buckets that smell horrendous driving down our roads.

I recommend doing what NJmax suggests.