I keep getting code 34, its installed on a 1986 280zx turbo using the 280zx turbo det sensor. I am guessing that is the issue.

But would also like to confirm a few things.

What is the unloaded voltage supposed to be, I am getting 3.8vdc from the wire harness pin 21 to ground. 

With a 700 ohm (that is what the 280zx knock sensor ohms out too) the voltage drops to about 100mv or about .1 volt. 

For fun I used a later model knock sensor (2 wire modern type that ohmed out at 500k) and the voltage drop was to about 2v

For those of you that have a 1986 300zxt, I would like to know what the unloaded vs loaded voltage reading you are getting at the sensor. 

here is a link to the project

 

quick update, I went out to check it again, the loaded voltage with the 280zx sensor was more like .06 vdc not .1vdc.

I disconnected the battery to clear the memory and tried the later model KS that was 500k resistance (2.0vdc loaded reading at the sensor when plugged in) and now the code is no longer flashing. I can only assume it still is not going as is a 22060-30P00 or a flat response sensor. I will see about getting the correct resonant type for it.  

So does anyone know the correct knock sensor for the 86 300zxt ecu that will fit the L28et head?

Edited May 17, 2024May 17 by Dave WM

videos

 

All of that is above my "paygrade" 😉

will be doing some more test (I love the test stand for this reason). the plan is to find a correct sensor for a 300zxt and check for fitment to a L28et block, then scope it while running in the engine, compare to the doughnut style I am currently using that does not set the code. See how they compare. I would like to actually see the ign timing get retarded by a simulated knock, I tried using a timing light and lightly tapping the block next to the sensor, could not see any change in timing, but that was at idle, and I have no idea of the strategy the ecu uses. I considered a band pass filter, as seen on another site, think it was hybrid Z, to narrow the freq response to about 6-7khz (the presumed freq created by pinging). Not sure exactly how that would work out, I presume I would just need to make sure I use a terminating resistor to avoid setting a short/open code. 

Before going down that route it may make sense to just abandon the idea of using the ECU for knock sensing and go with a stand alone knock sense control.

anyway just more reason to delay the engine install 🙂

I took a trip recently (800 mile round) it burned about 1/2 quart of oil and I got 27 mpg (mostly AC off) going about 65 most of the time on non ethanol. Not bad for a 50 year old car...

Needless to say the car ran perfectly and I did get a few chances to test the speed limits out on the turnpike (going the speed limit is insane there, you will get run over). The car loves to run over 80 mph.