Replace Knock Sensor
 

It is possible to replace the knock sensor without removing the intake manifold. There are also a few u-tube videos on how to do this. Using a 12 mm, six point, 5/8 drive flex socket (not a normal flex drive with a separate socket; that is too high) and about 15 inches of drive extensions, I did it in about 30 minutes. Most of that time was observing and thinking about how to do it. Also, I did it without getting my hand underneath the manifold, since on my 1996 Maxima, there was an emissions device blocking that area. Use a piece of paper to hold the bolt in place and the connecting wire to balance the socket while you find the bold hole. Then spin the extension with your hand while the bolt catches the threads. It at first seemed impossible to do, since I could barely see the bolt. The two repair shops both wanted to remove the intake manifold to do it. The motor now runs much crisper and I have no engine code now.

It is possible. Find some one with small hands. Lol also a magnet helps in removal

It is well known that 95-98 Maximas it's doable, 99 no way. A quick search would have told you this. :)

Yes, I first found the other posts and shared my experience to try to be helpful and show that an average mechanic like me can change the sensor.

;-)

https://maxima.org/forums/4th-genera...ast-night.html

Here is a link to a thread I made when I did the job.

The replacement videos and thread information posted above are all good. Nice Job!

This may be of interest to California Spec owners.

A few months ago, I wanted to test a new knock sensor without going through the pain of going under the LIM to replace it. So I bought an additional harness and relocated the KS to the UIM. The test worked great. Since the KS seems to like its new home, I'm in no hurry to relocate it back to the valley.

http://i286.photobucket.com/albums/l...ensor_Test.jpg

Although I didn't realize it at the time, it turns out the KS relocation is a common practice among Z32 owners. Oh well - I've been known to apply a few Z32 tricks to an A32 over the years. Why not?

Here's a couple of videos that shows how this occurs on a Z32.

It is very possible to replace the knock sensor without removing the intake. All kidding aside, you do need to find someone with small hands, I had my son heip me when I did it a few years ago.

I will add to the thread that if you replace this sensor clean with degreaser the area around the KS.

Anywhere there is a ground (such as the area around the KS)the dirt can build up and cause a voltage drop. I doubt youll get any issues here but a clean engine equals a clean ground.

My 97 Max was a Cali car and while it was possible to do without removing the UIM, the extra pollution controls, specifically the mounting brackets, made it a painful, bloody experience.

so, good times in other wards??:p :chuckle:

I just did this on my 99 when I pulled the engine. The 99 has a bunch of extra junk in the way of the valley - seems like there are vacuum hoses and stuff that aren't there in the older 4th gens.

We used a universal joint on the end of an extension to get to the bolt on top of the sensor. You can pull it out using the harness once the bolt is free, but getting it back in was a real pain.

My friend had this long mechanical grabber (has a thing like the claw machine at the arcade on the end) that was pretty stiff. I moved the sensor back in place with the grabber, being careful not to drop the bolt. I got the bolt (painfully) positioned and then he cranked it back down with the u-joint socket while I held the sensor in place by the harness plug (using the grabber, of course).

Not sure how you'd do that without pulling the engine... We needed a fair amount of clearance and had to work from two different angles at the same time. I like the idea of relocating the sensor.

This sensor reminds me of a mummy entombed in a pyramid somewhere :D You can look in there and see it but good luck getting a hand in on the 99.

ha!! 95 to 99 you need girlie hands to reach in and get it. i know a member in here that had their kid help them get it out. troo story......:nod:

You need surgeon's hands. :D

But if you have a Cali car, you'll think you picked up the wrong end of the scalpel.

Beware of some aftermarket knock sensors that don't appear to have any internal (shunt) resistance. Test (as per FSM page E242 - Test B Check Input Signal)

PIN2 to mount base of knock sensor (ground) or PIN1 should be around 500-620K ohm.

This can NOT be measured from the harness (as there is only a single wire to the KS). BUT if you have around 5 volts (at idle) showing across the harness pairs then this confirms the KS is either faulty, not grounded, or no shunt resistor...or harness connection to KS is faulty.

The shunt resistor DROPS the ECCS supplied reference voltage from approx 5 volts to around 2-3 volts. It's a single wire sensor with voltage bias.

http://www.diycardoctor.com/knock_sensor.htm

The shunt resistor in the KS is vital to notify the ECS that it's attached. No shunt...no voltage drop to the designated running range.

Result: ECS sets a 0304 code (P0325) but does NOT trip the CEL (dash warning light).
A reduced performance mapping (richer and less advance) is applied, causing rough running and low RPM hesitation (espec. noticeable on hot days).

Even if the KS is otherwise fully functional in providing AC voltage signal due to knock, the ECS considers it faulty as reference voltage remains high.

I saw absolutely no reference to this over many years of forum postings re: Maximas and KS postings, along with "I replaced my KS but I still get 0304/P0325 DTC's".

If you do have a non-shunt KS, then can fool the ECS to accept it by inserting a 560K ohm 0.5W metal film resistor at the top harness (back probe it) ..ie across the grey and the "white" but on my '98 it's a transparent case showing a copper stranded (shielding?) thock wire that goes down to the KS.

Result, no more codes and the correct dropped voltage appears at the harness.