# Check Engine Light



## hyethga (Jun 13, 2005)

I never was a pro when it came to these things but just today my car's "Check Engine" LED came on and I'm guessing, due to the sheer majority of the new threads on this forum, means that my O2 sensors/knockers got knocked out, so to speak. 

If anyone can take the time to just explain what to do and also briefly talk about the O2 sensors, I'd appreciate it. 

I had another friend whose "Check Engine" light came on his '97 Maxima but soon turned off. Does it come on routinely, so as to signify the drive to get his car checked and have routine maintenance done? If so, how do I reset it?

Thanks in advance.


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## N1ssanmax1 (Aug 1, 2005)

Well to start out I would go the Auto store and have them pull the code.....its free. And most of the time they can tell you what the code means right there. I wouldnt just jump to the knock sensor, but it could be.


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## brianw (Feb 25, 2004)

vbmaxima.8m.com has instructions on how to pull codes manually.


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## DRUNKHORSE (Mar 6, 2005)

Do as stated above. go to vbmaxima.com and pull the codes yourself. Once you have the code(s) you have several places where you can check what the codes mean. Vbmaxima has codes, HOWSTUFFWORKS also has codes, ans Autozone.com does too. Autozone will tell you what the code means and it will let you know what things to check.

What did you want to know about the o2 sensors? click here

*Oxygen sensor symptoms:*

Surging and/or hesitation(especially upon start up)
Poor or a decline in fuel econmy 
Failed exhaust emissions testing 
Premature failure of the Catalytic converter (rotten egg smell) 
Indicator "idiot" check engine lights coming on


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## fgoodyear (Mar 18, 2005)

The check engine light onMy '99 Maxima has been going on and off for a few months. My code says it is the two downstream sensors. On a good tester it says that the heaters are off. The light then goes back out. When I have it checked after the light goes out and stays out for a week or so, the codes have erased themselves. The downstream o2 sensors do nothing. They are a backup to tell the computer that the front ones are working. They don't affect how the engine runs at all. Mine does it when the weather gets cold. Whwn the ambient temp goes up....... the light goes out and it clears the codes. If it goes through a number of drive cycles without it kicking the code, the computer clears it own code. It's crazy, but at over$100 a pop for the sensors, Its not going to happen until I have to do it. The '99 Maxima has 4 sensors, but the code will tell you exactly which one it is. It will be bank 1 or 2 and sensor 1 or 2. bank tells left or right and sensor tells front or rear. 1 is front and 2 is rear. Good luck.....


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