96 Q45 Knock sensor issue with CA smog check

[dubs96q45]

I have searched the old threads and have been unable to find any posts that address my specific situation, so I apologize if I missed it somehow.

So here is my situation:

My California registration renewal required me to get a Smog Check for my 96 Q45. I took it to the nearest Check-only station, and before officially starting the test, the tech plugged a hand-held diagnostic device into my ECU. At this point the tech told me that I was showing a knock sensor code, he not any more specific than that. He did not complete the test because he told me that it would automatically fail, and that I was better off getting it fixed first(he was obviously not the owner).

I was quoted about $800 by Jerry Tucker's All Import shop down here in San Diego, which I didn't exactly have, so I began investigating other options. I came to the conclusion that my immediate solution was to get it tested and have it fail to get my registration renewed, and deal with the DMV. I was attempting to find a shop that also did repairs in hopes that I would be able to avoid paying for the smog check twice. After driving to and receiving bad info from no less than 6 shops, I finally called Hillcrest Auto. I was informed by the younger girl who I spoke to(no offense, just a little ironic), that Nissan/Infiniti of this era have a knock sensor code issue and as long as my check engine light is not on, it should not cause a problem with the smog check, due to the fact that this glitch is exempted by the CA Bureau of Auto Repair. I took it to the shop she referred me to, and it passed no problem(I will be going there from now on).

First of all, since I didn't find anything on here about this situation, I thought it was worth posting my experience so others don't go through all the hassle I have trying to get this issue resolved, only to find that it wasn't an issue at all.

Secondly, I was wondering if even though it doesn't present a smog check issue, and i have not had a noticeable change in MPG or performance, is there any reason to think that this could still be causing damage to my engine? I noticed a bunch of posts talking about a need to change the knock sensor and it associated components eventually, but I was unable to determine if this is one of those situations. Any info would be much appreciated.

My Q has 136k mi. approx., and prior to me the only other owner was my father, who took exceptional care of the car. I believe that the fact that after 2 years and 10,000 mi. and no maint. other that oil changes is evidence of this. He drives like an old lady anyway and this was his baby.

I apologize for the long post, but I hope it will save someone else from going thru the same hassle I have.

Thanks!

[unknown007]

If you have one you can clear the code.Im sure once you clear it from the ECu it wont show.I would do that and smog it then go into fixing it.Just something I would do but I didn't have an issue with mine but then again I got a 93 good luck.

[qship96]

Unless you are running timed race intervals on the track, you will not notice much difference on the road with good vs bad knock sensors- not much if any difference in mpg either.Get them replaced when you can, like when you need to pull plenum for hose leaks.Non functioning knockers will not damage your engine at all.

[unknown007]

Best bet is to do the knock sensor test and check them.If they are bad maybe someone can clear the code for you at a shop or something.Smog it then remember to replace them if anything under plenum like qship said needs replacing.

[Infinitiguy19]

Even if you clear the codes unless done right before the smog test, even then its risky and possibly a crime.

I wonder how long it take for the ECU to relearn the codes, I will check and see tomorrow to be for sure then i will post the results.

[unknown007]

A fellow student in my class deleted the codes from his BMW and my teacher said it usually erases it permanently.He usually also says drive it for a day or two to make sure it doesn't come up.Oh wait I've done it I had a revolution sensor code.My car seemed fine so I erased it drove it for a couple days and hooked it up 3times after that and it never came up again.If it was to really be a failure it would come up again.

[maxnix]

By all means erase the code and monitor.

You don't reveal previous maintenance history, but I bet it is ready for the infamous under plenum rehabilitation.

No fresh fluids or filters other than oil in 10k? Full service including mechanical ATF and PS fluid exchange at 90K?

I bet the old man was not driving on dubs.

[goody90q45]

You have a 96Q which is OBD2 so there's no hiding of codes from the smog gods. Even though you don't see a CEL the ECU is going to store any faluts or evidence of resetting for a long time. Those of us with 90-95 living in CA with a dead knock sensor or 2 can pass smog with flying colors because the smog computer doesn't read the Q's OBD1 computer (ECU) or its codes. They only check to see that the CEL is not on.

I think you need to ohm the KS to determine if they're dead or throwing a code for some other reason. It's simple to do with a voltmeter and why not ohm your fuel injectors while you're there for peace of mind. The KS will ohm in the 550k resistance range (alive) or they'll ohm infinite (dead). Fuel injectors should be in the 12-14 ohms resistance range.

If your KS are still alive then there is some other issue causing them to have to work and store a code. It they're ohming dead you'll need to replace them to pass smog. Let us know what you find.

[qship96]

On the 96Q you can clear the knock sensor code with a generic obd2 code reader, but code will come back the next time you start car- it will NEVER illuminate the check engine lamp.

You can search my posts from Nov 08 documenting my MPG on my 1400 mile round trip from Baltimore to Atlanta on non functioning knock sensors, and compare to return trip after T3 replaced the knock sensors, 200,000 mile old front oxygen sensors, 133,000 mile old sparkplugs, along with other work- the MPG difference may surprise alot of owners.

As far as difference in engine power, the main difference I felt with the new knock sensors was better tip in response under light /mid throttle{ like when you are maintaining speed around a curve at low speed and lightly depress gas petal upon exiting a curve}