I got 0303 and 0304 on ECU, then I followed the instructions in "sticky" to reset the ECU about a month ago. The check engine light has been off and has not come on since.

0303 and 0304 are for knock and oxygen sensors. Are they both like one-time-use? Is it possible they are still good but the check engine light came on because they once detected a fault, and now the faults are gone so the check engine light is off while both are still good?

If the fault is still there or the sensors are bad, will the light come on again?

Thanks for any opinions.

 

If they were triggered, then you should deff. look into it.

 

my car started shuttering, then the CEL went on for my knock sensor. I obviously changed mine. If there doesn't seem to be anything wrong, check em out and if the reset of the ecu turns em off, you can just pray that they're fine. People seem to debate whether changing the knock sensor really does anything. Personally, I would change it though.