LeX2K

Where did you buy them?
Oscilloscope is required to view a knock sensor signal.

Margate330

This is true because I think the 1mz and 3mz engines uses piezoelectric sensors.

All I know is they look like sound wave signals(plus some noise) when I scoped mine and someone would need a keen eye to know if the waveform is good or not.

The Engine ecm knows what a good knock sensor output looks like but I couldn't, just looking at the scope.

350zGuy

I can see the fluctuations in the voltage but I guess no one knows what those voltages should look like. I’m just gonna see what the denso sensors do. Hopefully they fix it, if not, I guess I’ll just ride with my scanner connected while I drive like I have been. This is my beater so I really don’t care but it would be nice to have OD again without resetting ecu, turning car off/on while I’m on the highway, and hoping I don’t have to come to a stop anytime soon 😆

LeX2K

Interesting that you refuse to say where you bought the Denso's.

350zGuy

from a Lexus dealer online. Sorry. I figured the Dorman brand sensor would be more important for the information I was looking for. I’ll keep you guys posted when the denso sensors come in. Also, I appreciate your response. Didn’t see the email saying you did so I completely missed your input.

salimshah

Unlike other sensors, this seems like an analog signal ... very much like microphone output when some one speaks into it. My educated guess is the ECU is matching sound at tdc/ignition/cam position. The sensors is shaped to enhance certain frequency vs the mic which is designed for full audio spectrum.

Salim

Margate330

You just gave me a good idea. Lol

I wonder if the Engine Ecm can be tricked by a simple program running on a cheap $10 microcontroller.

This would be for a double knock sensor fail work around.

If I ever have free time to play with it I might do it just for fun!

LeX2K

That's a great way to melt pistons. All sensors are analog BTW.

Margate330

Yeah, that's a good point, it would work for clearing the check engine light if the Engine Ecm can be fooled.

But, the knock sensor feedback is important as everyone knows because the Engine Ecm uses the signal to adjust the timing.

I believe the Engine Ecm could be fooled by a microcontroller PWM to analog output to mimic the knock sensor. Depending on the voltage levels of a good knock sensor, maybe some minimal supporting components.

Dam, it was just a theory! Lol

350zGuy

hey. I got the car for free so I don’t really want to drop a lot into it. I’ll beat around for another year or two and I’ll be happy.

Margate330

Hi,
Like @LeX2K was saying above, damage can occur.

I have a failed knock sensor too and I'm currently running both knock sensor Engine Ecm inputs off my only one good knock sensor.

I need to get busy and replace the bad knock sensor before my only good one fails or I'll be really mad at myself. lol

LeX2K

I suggest buying the knock sensors from Amayama so you have them on hand since prices keep going up.

salimshah

Word of caution:

Don't buy any OEM knock sensor. Take the VIN to confirm the right part at time of purchase.

Salim

Margate330

Last I checked a year or so ago, my local dealer was wanting $300+ each for these if I remember.

I've been waiting for members to claim raving success with an aftermarket knock sensor but no such luck yet. Lol

salimshah

That is the very reason this hack is popular. And there are number of gaskets + labor involved.

Salim