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Knock sensor in my 2003 nissan xterra

so just got this 2003 nissan xterra, 4x4, V6, 5-speed, SWEET truck, but is showing a pending code, knock sensor

1) should i care, because the check-engine light is not on?

2)what exactly does a knock sensor do?

3)the cost to repair (need to take out the intake…EEEEEEEEE…) is around $800! i may be able to do it myself…but…

The knock sensor detects if predetonation or pinging is occuring in any of the cylinders. If this does occur, the engine management system adjusts the ignition timing and the injector pulse widths to eliminate the pinging. If this is a pending code, I wouldn’t worry about it. It means something occured in the past with knock sensor that the engine management didn’t like, so it stored a pending code. As long as the Check Engine light doesn’t come on, there’s nothing wrong.


THANK YOU tester. but don’t the injector pulsations effect engine performance?

Clear the code (reset engine computer)and see if and how soon it comes back.

did that, and peding code came back within 2 months, still no check engine light. i have heard that this may be a common problem with xterras. found a place that would do it for $500. what do you think? does the sensor respond to ignition issues related to the quality of the gasoline?

Are you using the recommend octane fuel? If not, then I suggest switching to the recommended octane.

Unless you have to pass emissions testing, you need not throw money at the problem. The fix for the problem isn’t an automatic parts change, anyway. A shop which says that they will simply change out a part, without verifying the need, isn’t doing you a service. In fact, they are doing you a disservice.
Use a higher octane gasoline, and use a throttle body cleaner to help clean up the top (internal) part of the engine.
There can be a number of causes for ping. A good shop will check for those. A bad shop will just throw parts, and your money, at the problem.

In the days before knock sensors a little “knock” now and again didn’t hurt anything. Heavy knocking could blow a hole in a piston. Even if the knock sensor wasn’t working you can still hear an engine that is “knocking”. When you hear it you just back off the throttle a bit and/or downshift to maintain or increase speed and take some load off the engine. On your next fill up use a higher octane gasoline.

Are you pulling a trailer? Do you live in the mountains? If so you may use a high octane fuel. I don’t know what your owners manual calls for but use whatever it says.

Some cars say premium preferred and the knock sensor will read that you are using regular and pull back the timing a bit to avoid knocking. Premium required cars either do not have a knock sensor and can’t retard the timing or just flat out need premium due to high compression.

The knock sensor isn’t that critical if you use the recommended fuel. My guess is your knock sensor is actually functioning. Why it is sending codes is a mystery but I don’t see it as a big deal and not worth spending $500 to $600 dollars on. You may change out the sensor and still get the codes. In fixing the sensor you got guys in there messing with your cars jewels. I don’t want anyone messing with my jewels unless absolutely necessary.

I do live in utah, so do some high elevation driving, and plan on pulling a small tent triler come summer time. so, i will start using the mid octane (88, i think) fuel and see how it goes. this gives me till november 2009 to run some experiments with basic maitenance. THANKS.

I had a knock sencer problem and all the books i have say to have you and a friend to help put a timing light on the engine and have your helper use a hammer and tap on the pass side exhaust maniffold when this is done you (using the timing light)will see the timing jump around if it does there is nothing to worry about.

OK…i’ll try that. the friend will be my wife! it won’t hurt her to get involved in automotive issues…to her credit, she actually likes to get into it. thanks dodge man!

I have worked on a couple of Nissan Maximas with the 3.0L V6. Do you have the same engine? Knock sensor failure is a common problem on them. The problem with not fixing it is that the engine computer will “play it safe” and retard the ignition timing all the time. This will reduce performance and fuel economy slightly.

The repair procedure for the 3.0L engine says that you must remove the intake manifold to access the sensor. I found that you do not need to remove it since you can get to the knock sensor mounting bolt with a swivel socket (12mm I think)and a long extension bar on the ratchet.

I’d go with Markmask’s suggestion. The knock sensor cost about $50 at any auto parts store. The dealer is using the factory repair manual which is designed to make parts replacement as easy as possible for dealer mechanics. If you’re willing to exert yourself (or, a novice mechanic) a little in tight quarters, you could save hundreds of $$$$.
The knock sensor should output 2.4 volts dc. Here is the wire color, PCM pin #, voltage, engine speed information: