Please help! When I got in the car to go home just now, check engine light came on. so, i check the ECU error codes and gave two codes: 05-03 (front right heated O2 sensor) and 03-04 (knock sensor). after checking, i reset the ECU. after the ECU reset, the car idle really low (300rpm) then dies. to restart the engine, i have to crank and hit the gas pedal otherwise the car won't start. this is weird since the car ideled just fine before the ECU reset, although check engine light was on.

PLEASE HELP! Any insights! Is it at least safe to drive home? or is that going to mess up my car?

thx in advance!
jhlee

 

Yes, it is safe to drive home, granted it doesn't stall out initially. You only need to replace the O2 sensor since the O2 sensors through an automatic knock sensor code when tripped. The sensor is Bosch (OEM) and is available at Autozone, www.foreignpartsplace.com , Pep Boys, etc....

BTW, how many miles are on your Maxima? IF you have more than 100k, you also may want to look into replacing the knock sensor anyways.

 

thank you for the insight. i have 93k miles. i took really good care of the car, but ever since i started moding my car, i've been getting little problems...this one being the worst to date.

is there any possibiliy that this problem is related to the electrical system? the reason i ask is that, yesterday i added a high current 3rd amp to my stereo system and just finished with the install this afternoon. i had an hour to test out the new stereo system while driving, but everything was fine this afternoon.

jhlee

 

UPDATE:

this is weird. the car idles fine now and i was able to drive home without a problem although i didn't do anything to the car except reset the ecu. furthermore, after i reset the ecu the cel didn't come back while driving home.

i was afraid to push the car so i babied it home. if there is still no cel tomorrow morning, i'll drive it hard and see if the cel comes back on. if the cel doesn't return, do i still need to replace the O2 sensor? please help!

jhlee

 

if it doenst come back on, i wouldnt worry about it...but itll probably come back on ...change the o2 sensor first if the CEL comes back on, then reset the ECU, and drive around for a few days...if the KS code is still there, your gonna find yourself spending another 130$

 

When you reset the ECU it has to relearn how your car's engine runs. That includes the idle. You case was a little worse then others. Guess you have a really dumb ECU kidding.... If that sensor is bad, the CEL will come back. After you replace that sensor and reset the ECU, don't be suprised if your car idles strange again while the ECU gets up to snub again.

 

I drove the car pretty hard this morning and no CEL. I guess everything is okay. Except I noticed that I'm getting really bad gas mileage. I'm down to a quarter tank and only have 200 miles on it. I usually get 250 miles by this time. Isn't poor gas mileage a sign of bad O2 sensor?

jhlee

 

Yes, a bad O2 sensor got me bad gas mileage. Second bad O2 sensor caused me to get really good gas mileage but the car had less power Both O2 sensors tripped the knock sensor code as well. Good luck with it!
-Chad