Member Credit: Sparky
Code P0325 stored in 1997 Nissan Maxima. Because the knock sensor is normally at fault I usually test it first. The knock sensor is located under the intake and is accessible on the driver’sside of the car.
Locate the knock sensor subharness connector. It is near the dipstick tube, red knob in center of above picture.
Disconnect the sensor and check resistance from terminal #1 (white wire) to engine ground. resistance should be between 500K -620K ohms. If the resistance is not within the specifications the sensor and subharness must be removed to do further testing. If it is within specifications recheck while wiggling the subharness wires. If still no problem is found the wire between the computer and the knock sensor must be checked for opens or grounds.
In this and in most cases it was not within specifications. Now comes the tricky part, the labor guides give 2.9 hours to change the sensor and it requires removal of the intake. I have a short cut if you have some tools and patience it can be done in about half an hour or so. I always try to see if I can break the attaching bolt loose with a swivel socket and extension. If it does then great ,simply remove the bolt and use the subharness to pull the knock sensor up and out. DO NOT BEND THE HARNESS . You need to keep it in it’s original shape to reinstall the sensor without any difficulty.
If the bolt will not break loose easily, what I do is with the help of a telescoping magnet, I lower a long 12 point boxed end wrench into position on the knock sensor retaining bolt. Then I use a long skinny screw driver to hold the wrench in place while the magnet is removed.
Then while keeping the wrench in place with the long skinny screwdriver I put a heavy pry bar into position to use as a lever to move the wrench.
After the bolt is broken loos it is easy to remove with the swivel socket and extension used earlier.
With the sensor and subharness removed it is now easy to check the sensor. This one like many has an external split and tested faulty.
To install the new knock sensor, attach the subharness and drop the attaching bolt into the sensor. Using a long skinny screwdriver or a mechanics finger (actual name of tool) as a support and guide lower the sensor and bolt into position. Once you feel the the bolt drop into the threaded hole, use the harness to maintain this position. Next place your swivel socket and extension in place without moving the bolt from it’s centered position. Gently turn the bolt making sure not to cross thread it. It may take a few attempts. Be patient and very gentle as it will be a 3 hour mistake. Once the bolt is tightened with the swivel socket, I usually drop the wrench back in place and put a final tightening on it with the pry bar as outlined in the removal procedure. DO NOT OVER TIGHTEN.
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