I was happily driving along today when all of a sudden I notice my CEL go on. I was like, "crap!" When I get home, I check the ECU and get the following codes:

1.) 0304 = Knock Sensor
2.) 0409 = Oxygen Sensor??? (not sure though. The sticky's link doesn't work for me. Can someone please double check this for me. Thanks.)

So what do ya guys think? Is my dad to blame for filling up my tank with 87 octane gasoline, or is this just pure coincidence?

Another question: What if I were to NOT doing anything. I mean, what if I were to drive for a while and see if I get worse gas mileage and a loss of hp? It's not detremental (sp?) to my car's health, is it?

Sorry for the laundry list of questions.

 

0409 comes up as Undefined. Check the code again.

One tank of 87 shouldn't be a big deal.

I'd try getting a bottle of Techron fuel system cleaner, pour it in, fill up with 92+, reset the ECU and see what happens.

 

You can always just add a gasoline additive to help your car perform better while you are on that tank of gas. You could also try adding some race fuel (1 gal.) to help bring up the overall octane level of that tank of gas. I doubt you will have any long term, detrimental effects. Just try to bring up the octane level of the gas that's in the car asap.

 

I talked to a nissan tech about some codes I got a couple weeks ago, one of which was a knock sensor and the other were transmission codes, and he said that the knock sensor alone will never set off an engine light, so most likely that code you got is just stored from who knows how long ago.

Anyway, what I would do is wait until that tank is gone, then reset the light and see if it comes back on again.

 

Fuel additive? How will that help him? If he pours in that tiny bottle into 18 gallons of fuel it will raise his octane to 87.2 or less? Waste of $5 on that crap. 0409 IS a front O2 sensor. I'm guessing the O2 was bad all the time and the cheaper fuel just made it crap out completely. Get a cheap sensor from the group deal going or right now and that should make the KS go away.

 

The knock sensor WILL set off the CEL if it hears knock. Put some octane booster in and reset the CEL and it should go away.

It probably won't set the CEL off if it's malfunctioning, however.

 

It will not. If you're driving and the KS hears knock you still won't see the CEL light come on. You have to check the ECU in order to see 0304.

 

I took the snorkel off one day on an otherwise stock intake system and let the car idle in the summer heat for about 25-30 minutes. After a while of the intake sucking in all that hot a$$ under-hood air the CEL came on. Went home and checked the code, 0304. Put the snorkel back on, reset the ECU and the the CEL never came back. Knock sensor is still good.

 

Code 0409 is P0133 Upstream O2 sensor slow respone fault (right bank). The sensor is dead.

 

The light's off!! I called my dad and asked him to talk to one of his fellow mechanics at the car dealership he works at. One guy said that if the gas cap is not completely locked/clicked, it could trigger a CEL. Turns out that that was the case!! I tightened the gas cap, reset the ECU.... and BAM!!! No more CEL! BTW, I had already filled up my tank with premium 2 days ago after the tank my dad filled had been somewhat used up.

I don't know whether the problem is dormant and will return down the road (maybe the oxygen and knock sensors DO need to be replaced. The car does have 95k miles.) But I guess all is well that ends well!!

 

I suggest you replace the O2 sensors anyway since they are most likely on their way out.

 

But i got well over 400 miles on my last tank of gas. It's not like I'm gettin crappy gas mileage or sense a loss in hp. I'll probly wait until I need to get them replaced before replacing them. I am kinda short on dough right now anyways. If I can put this off for another month or so, I'm gonna do it.

 

Like Big D says, it does not. Most of us boosted guys would have set off a CEL if that was the case.

 

I know someone with a 96 max and has been only filling up with regular gas for the life of the car. Car runs perfect. In fact, I bet most other maxima owners that are not on the .org filll their car with regular gas and probably have no problems as well. I only fill up regular on my 98 and knock sensor is fine and engine appears to run just like day 1.

 

91 is recomended for OPTIMUM performance. Using 87 won't damage anything but will most likely cut down the engine life and stuff like that. If the engine is running fine and you don't experience bad knock, cars have subtle knock all the time but it's dangerous enough to set off the KS, it should be fine. With 93 octane you'd probably have a bit more power, slightly better gas mileage, and your engine wouldn't get as dirty and stuff inside cause of the cleaner gas.

 

for your dad using 87 octane in a Maxima

 

Loose gas cap!!! welcome to the wonderful world of obd-2. Iwould check the codes anyway to see if you have the KS code.

 

same thing happened with me, my mom put in 87 octane, engine light came on, and what i did was put 94 octane from sunoco, and a couple days later the engine light dissapeared and car runs fine now

 

Uhh can anyone confirm this gas cap setting off the CEL thing? It sounds kinda rediculous to me.

 

At least your car didn't die. I remember I went to get some gas with my pops, he was drving my car, so we stopped by CLARK which was on the way. He put in 93octane, good man, half a block later my car dies. Get a KS code and O2 code. The car fired back up but ran like ****. Spent the next day burning off half a tank just so I could put in some AMOCO.

 

A loose gas tank cap will not trigger a KS or an O2 sensor code, but an "evap emission" code. Of course, resetting the ECM will turn off the CEL.

I say drive a couple of cycles, and your O2 sensor code will come back. Change the O2, but not the KS yet. Drive another couple of cycles, chances are the KS code will not come back.

 

When I first purchased my 95 max 4 years ago, I used regular all the time. The car ran fine. However, after a couple of months I would get the knock and 02 sensor code all of the time. I switched to 93 (no 91 in NJ) and after a few months I stopped getting either code....but it took a while.

 

Oh ya...I should also mention that the knock sensor code did come back, but only becuase the rear O2 sensor needs to be replaced.

 

I agree that one tank of 87 should not have done this. It is probably just coincidental.