Knock sensor

engines
lights
sensors

#1

I have a 2000 Infiniti Q45 with a “check engine” light that, after analyzing, a mechanic said I need at one but preferably two knock sensors at a total cost of $1,000. The car is running fine, but if I don’t replace them will it hurt the engine?


#2

Infinitis certainly are not inexpensive to maintain are they? You might not do damage by not replacing it because it might go into a relatively lower state of tune to prevent knocking. This will cause fuel economy and performance to suffer. The other problem is the CEL. If it is always on, at least until the bulb burns out, you won?t know if there is another problem with the car.


#3

One has to wonder, how much analyzing the mechanic did. For all I know, he just read the trouble code, which contains the words KNOCK SENSOR, and decided on that, alone, and nothing more, to replace the knock sensor(s). Knock sensors don’t fail that often.
Take it to a mechanic who will do the necessary knock sensor CIRCUIT testing, before deciding to change a knock sensor(s), IF needed.
Bring the trouble code here for us to have a look-see.


#4

Even if the sensors are bad I would have to wonder about the very high charge to replace them. It may be due to a lot of labor to get to them. I would have another shop check things out.


#5

what mechanic? what kind of shop? diffylube?

sounds fishy to me


#6

my opinion is that you should drop by a local autozone, checkers, etc and have the car scanned. post any codes you’re given back here for discussion.

your engine will not be damaged by faulty knock sensors unless you’re having a pre-ignition problem (denoted by a rattle when the engine is placed under a load; uphill, passing, etc.)

the only thing the knock sensors do is provide a signal to the ecm (computer) if pre-ignition occurs and the ecm will in turn retard the timing enough to offset the rattle that occurs (up to a point).
this is all done lightning fast and is variable.

i’m a bit suspect about why he wants to replace both since that could denote some guessing.


#7

These can be tested by attaching a timming light to your engine then lightly taping around the knock sensor with a hammer. If your timing then retards when tapping then the knock sensor is good. If it don’t then it could be a bad connection between the knock sensor and the ECM.

I would make sure that if your mechanic buys and installs these two knock sensors and that doesn’t take care of the problem then he shouldn’t charge you for them!

Here is your cost for the sensor:

Now times that by two since he is wanting to replace both of them. Your cost for parts would If you bought them would then be $278.98 plus tax.

Are these the only codes set? Could be something else going on that is causeing your problem.