I would have searched if I could but I can't...

I have almost 118k on my 96 Maxima and today the CEL comes on for the first time. Codes 0503 and 0304. I know the 0304 is the Knock Sensor and the 0503 is the FR Heated O2 Sensor, but what made both of these come on at the same time like this? I've always been told that when a CEL is shown, it's not necesarily the sensor that's gone bad but something that's making the sensor read bad readings. What could be wrong that would make my ECU throw these codes?

If I have to replace these sensors, how much is it going to cost me?

Thanks...

 

if im not mistaken, i think ive heard that if an O2 sensor goes out, it can trip the knock sensor also. so the knock sensor is just a dummy code. somebody correct me if im wrong. and as far as price for the O2 sensor, they run around $80 at a parts store and over $100 at the dealer. but check this out O2 sensor

 

wow those are good prices.

 

Yea, free shipping also!!