95 altima o2 and knock sensors


Old 04-18-09, 01:37 PM
simelina's Avatar
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95 altima o2 and knock sensors

My check engine light has been on for 2 weeks. I have upgraded to the highest gas available, thinking that was the issue. It takes longer than usual to accelerate, plus, about 6 months ago I was having to put brake fluid in every 50 miles or so. The brake light doesn't come on anymore, but the check engine light wont go away, lol.
I went to autozone for the comp. it gave two senors, o2, sensor 2, and knock sensor. First off, I have no idea what either of those are, but my question is.... Which do I change first?
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Old 04-19-09, 09:05 AM
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Sounds like you had a pretty significant brake fluid leak for starters. Did that go away on its own?

O2 sensor is oxygen sensor, used to electronically adjust the fuel mixture for optimum performance. Knock sensor listens for evidence of spark knock/ping and automatically adjusts ignition timing for best performance.

Buying more expensive gas won't fix either problem. Replacing either the O2 or knock sesnor (or both) won't necessarily fix the problem either because often related items/problems will give a code for an associated component or related problem.
As many miles as is probably on your car, an O2 sensor may not be a bad investment, but be prepared as some of them are a little pricey.
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