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Discussion Starter · #1 · (Edited)
So, i have that code set into the ecu...

i searched a lot and a lot of different info came out...surprinsingly enough, most of them are wrong from the start, there is so much miss informed peoples on the planet:lame:

I found part of a post where it shows the test procedure for the knock sensor, to measure resistance in between terminal 2 and ground,...

I am automotive electronic engineer, i know every single aspect of any sensors and their functions and EFI strategy...a knock sensor is a microphone made of piezo electric ceramic element, so it shouldnt measure ANY resistance at all !!! unless they put a resisor into it. The signal is filtered into the ECU to monitor only high pitch "pinging", and then will make the ecu retard the timing a bit and adjust its fireing/fueling tables accordingly,...

I came over all kind of knock sensor in my life, bosh, denso, ford, gm, vw, BMW,...they are all the same inside: just a plain piezo element.

So why do they suggest to measure the resistance ?? it should realy read infinite, which exactly mine does, but truly measure and act like it should.

I scoped (digital oscilloscope) the signal when the engine runs, i can see all the cylinders explosion and when i tap on the intake with a soft hammer i can see the signal as well, so then sensor is good imho.

So why does it set the code ? (the CEL is not on).
=> it dont say that the right cylinder bank suffer from pinging, it says the sensor is defective, which is totaly different. Or could it be the same code that is set then ??

The 02 sensors are all fine, the engine runs like a champ, no ping, no metalic sound or loose parts sound. it has 120 000km and has never been abused.
I have a wide band 02 meter and i have probed both bank, the mixture is exactly like it should, so its not a lean condition problem.

I also checked the ground loops and ground loss voltages, its all fine.

If you have any info to shed a bit of light on this, let me know !!

EDIT: there was a broken wire that caused intermitent signal. After a bit more search, there is effectively a resistor in the sensor so the ECU can check dynamicaly if the sensor is present or not, otherwise the ECU cannot see the sensor since the piezo element has an infinite internal resistance. The resistance is around 500k ohm (500k-700k at 20 deg cel.). With the ECU intenal resistance, it creates a voltage divider, thus still allowing the AC signal of the sensor go thru unaltered, by reading the DC voltage the ECU "knows" that the sensor is there or not.

The fact that mine reads infinite but still gives a signal shows that only its internal resistor has went bad. So i did put one external of the proper value and it is good and running. No more code set.

Hope that will help someone...
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