Twice in the past week I have hit a pothole and had my service engine light come on. The computer at Advance Autoparts gave me a code for the knock sensor both times. Is this the sensor going bad or something worse? I used to live in New England and the underside of my truck shows the wear and tear of salty roads. Could all the mounts be shot because of this and not cushioning the engine enough, causing the sensor to trip? Also, I think I need new shocks/struts (haven't been changed, 105,000 miles on the truck). How about this causing too much shock?
The job of the knock sensor is to detect the vibrations of engine "knock" caused by an advanced ignition system. It allows the fuel mixture to run extremely lean and efficient and when it can't perform at maximum effeciency, it "knocks" like it has bad gas and the computer gets the signal from the sensor and changes the ignition to ****** the spark and make the knock go away. If the computer is confused by the signal (too much signal, no signal or too frequent signal) the computer flips the light on with a 0402 code.
If you hit a pothole and the light goes on it might have got too much signal. If it starts going on at other times, you may have a sensor that is sending out too many signals and it might be from bad gas that the computer can't control the knocks.
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Re: Knock Sensor 2002 Nissan Frontier
It's a good possibility that's what's happing, if that's the only time the light comes on,cause it detects any vibrations in the engine,and if the truck is really hitting the pot holes bad, yeh, it would trip it. I would have the motor mounts checked while your at it too.
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I'm willing to bet you have weak upper O2 sensors & there's nothing wrong with your knock sensor. But if you want, the knock sensor is under the lower intake manifold in the back that is located under the upper intake manifold also called the upper plenum. The lower intake manifold is wedged between the 2 heads and is an enormous pain in the azz to get to. You can check the O2 sensors with a scanning tool that will show you the upper sensors in bank 1 & 2 bouncing electrical current from about .5v to 5v several times per second. Anything less show weak sluggish sensors. The resulting lean mixture causes a knock. Change the sensors and the knock goes away and so does the engine light after you reset it. It took me 6 months to find this problem after replacing everything else including the 6mth old O2 sensors fresh from China. Now I have Bosch. PS The lower sensors went 2 weeks later & I was told any more problems it's the fuel regulator. 2001 Frontier 3.3l v6. No problems since, it purrs like a kitten. I'd suggest the Bosch, it's a special design for that 3.3l engine.
Bypassing (hotwiring) the knock sensor will remove a signal the computer needs to operate. Unexpected results for sure , possible damage to the computer may result. Replacing the knock sensor is the best way.
The pcm uses the knock sensor to monitor for engine knocking, and adjusts ignition timing based on this. If there is no knock sensor present, you will wind up with a hard fault that will keep the check engine lamp on continuously. Also, the truck will go into a more conservative driving mode to prevent knocking. The knock sensor for a frontier is not terribly expensive, but it is a pain to access on nissan v6s, under the intake manifold
The knock sensor picks up vibrations from detonation and sends a signal to the engine computer, which then adjusts the igntion timing [ retards advance ] to correct it. You can read the operation of the sensor with a full function scanner, if it's working then you have to look for a physical problem with the motor causing the konck.
the knock sensor on a 3.5L should be just under the exhaust ports on the right side of the engine if you're facing the side with the pulleys and crank(front) for the life of me, I cant remember if the engine is mounted longitudinally or tranversely in the frontiers.....lol. There should be a wire going to a small black thing thats just kind of there,... its really easy to miss. if you can, check the nissan forums or somewhere online the e-manual that should have the exact placement of it in diagrams.
knock sensor is located on the block usually under the intake. nissan has problems with these sensors. i have chaunged plenty of these on nissans in the past year. this has no affect on your gas mileage. this sensor picks up misfires on the engine. sometimes you might have rough idle and can't feel it in the drivers seat but the knock sensor can. i would suggest maybe a tune up spark plugs, air filter, fuel filter first before going to take apart a bunch of things to change a sensor. the sensor is designed to pick up any differences in motor quality and will throw the engine light on. sometimes the problem is the knock sensor, or there is an underlying cause that the knock sensor is reading.
Well, you have another issue besides a knock sensor problem. A knock sensor code WILL NOT illuminate the check engine light. Check for other codes stored in the ECU. I have seen oxygen sensor issues cause knock sensor issues due to inaccurate fuel delivery resulting in engine ping at all times (causing the ECU to think that the knock sensor is bad because it's reporting ping at all times) - but also had codes for one or more O2 sensors.