Nissan XTerra Forum banner

221 - 227 of 227 Posts

·
Registered
Joined
·
11 Posts
No seriously, I'm not making this up, that is why the signal wire is shielded. Google knock sensor oscilloscope.
 

·
Registered
Joined
·
11 Posts
It's explained well here.


The fact the tech was confident back probing this wire without shorting it out makes me feel better about my resistor mod.
 

·
Registered
Joined
·
181 Posts
That says nothing about the ECU looking at bias voltage. In fact, the Ohms test he does in the second part of the video is what seems relevant to me. A quick google search tells me bias voltage is what the knock sensor needs to operate and says nothing about why the ECU would need it, as it has its own power source.

The fact that it's shielded is explained by the way a piezo device operates. Noise on the circuit could cause the piezo element to trigger a false positive, not that noise to the ECU will. Your explanation seems to be that the ECU has a piezo device or oscilloscope functionality. My explanation is that it has an acceptable resistance range it's looking for. The same as a temp sensor and many other simple sensors that have been used in automotive and other engine systems for decades.

I've implemented a mod on my old atv to correct a failing temp sensor using a pot to adjust Ohms read by the fan control module. Ohms is what triggers the FCM to kick the fan on, not voltage. It's not as complicated as you're making it out to be.

Also, if you think the knock sensor can still function with your resistor in the circuit says a lot about how much you understand how all this works. You likely have an open circuit past that connector.
 

·
Registered
Joined
·
181 Posts
I never said it was smart. It's a simple piezo device that changes the resistance in the circuit when it encounters noise and has a normal resistance of 540k when all is well.
 

·
Registered
Joined
·
11 Posts
I'm going to be as diplomatic as possible in a final reply. When it becomes patently clear to everyone around that a party knows little to nothing about DC circuits, signal processing and what a piezo electric circuit can and can't do. That party should summon every bit of humility and cease contributing to the conversation as it adds nothing and only serves to muddy the waters.
 

·
Registered
Joined
·
181 Posts
It really doesn't matter how the knock sensor functions to anyone here looking to clear the code. It's a fact that a code will be triggered if the ECU doesn't read 540k-620k resistance/Ohms on the circuit. The code will be for a failed circuit and not a knocking engine condition. The code can usually be cleared by replacing the sensor or with a 540k Ohm resistor. The later obviously will not sense a knocking engine to retard timing and protect the engine. The only one muddying the waters is you, by claiming that using a resistor inline somehow will still provide knock sensor functionality. That misinformation could actually be harmful to anyone who believed it and decided to do the mod based on your "contribution".
 
221 - 227 of 227 Posts
Top