300ZX (Z32) Forums Dedicated to 90-96 ZCars otherwize known as the Z32's

Detonation sensor w/ohms reading

Old 05-27-2014, 01:34 AM
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Detonation sensor w/ohms reading

Today I tested my detonation sensor connector (ecu side) with an ohm meter and I got 12.5 with the car off. The Car on acc. I tested again and I got 140.0
Now I read something that that it is supposed to read 500k ohms?? That sounds like a lot! So my question is with my numbers tested is my connector bad from the ecu or do those numbers sound okay? I was just going to relocate the entire detonation sensor and harness but if all I need is that top clip and wiring it would probably be cheaper on me.
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Old 05-27-2014, 10:54 AM
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Is your ecu throwing a code for the detonation (knock) sensor?

Last year on my 97 Infiniti QX4 I got the dreaded knock sensor code. After some research I found that since most all (if not all) VG engines have the knock sensor under the lower intake, the simple solution is to solder up a set of resistors from RadioShack that equal ~530k ohms and install it in the ecu side of the knock sensor harness plug. Relocating the knock sensor will give false readings.

Also, make sure you've downloaded the FSM: www.xenonz32.com/reference.html
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Old 05-27-2014, 12:17 PM
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okay so i did the resistor test and after i cleared the code 3-4 diffrent times it still comes back with a code 34. my question is, is the pack i bought the correct size? the guy and radio shack said it was a 1 mega ohm resistor so i sodered it up and tried the resistor trick. second is i mentioned before that after testing the connector to the ecu it didnt read close to 500k ohms, so maybe the connector going to the knock isnt bad, maybe its the harness that goes to the ecu? my other question is what is that harness called? is that considered the sub harness? thanks again heres some pics
Attached Thumbnails Detonation sensor w/ohms reading-front-1mega-ohm-resistor.jpg   Detonation sensor w/ohms reading-1-mega-ohm-resister-package.jpg   Detonation sensor w/ohms reading-resistor-jump-ecu-cable.jpg  
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Old 05-27-2014, 12:21 PM
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You need to solder up 2 of those in parallel, they split the ohms to equal 500k....just looked again, says 10mohm...thats not 1 mohm, to edit more, brown, black, blue IS 10 megaohms. Brown, black green is 1 mohm.

Last edited by Skully; 05-27-2014 at 12:25 PM.
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Old 05-27-2014, 12:50 PM
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Originally Posted by Skully View Post
You need to solder up 2 of those in parallel, they split the ohms to equal 500k....just looked again, says 10mohm...thats not 1 mohm, to edit more, brown, black, blue IS 10 megaohms. Brown, black green is 1 mohm.
okay, I figured that the resistor some how might have been wrong since I dont know much about them. It's tough for me to understand I guess.
So now my question is, which way should I wire them?
The one listed 2 wires or 1 wire?
and wiring (2) brown black blue resistors will be okay?

thanks sooo much for your help.
Attached Thumbnails Detonation sensor w/ohms reading-running-parallel.jpg  

Last edited by 97gtp; 05-27-2014 at 12:53 PM.
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Old 05-27-2014, 12:56 PM
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Originally Posted by 97gtp View Post
okay, I figured that the resistor some how might have been wrong since I dont know much about them. It's tough for me to understand I guess.
So now my question is, which way should I wire them?
The one listed 2 wires or 1 wire?
and wiring (2) brown black blue resistors will be okay?

thanks sooo much for your help.
If you wire the 2 that you have you will have 5megaohms. which is far from 500k ohms. You need brown black green resistors. And I would wire them like the second drawing, put a piece of heat shrink over top and seal them up.


And just to inquire, Nismo why would you suggest not relocating the sensor? I have done it fine with my 300zx, I know there would be a chance it could pick up other ticks etc, but better than nothing? So far no codes, or safety modes.

Cheers!

Last edited by Skully; 05-27-2014 at 01:03 PM.
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Old 05-27-2014, 01:03 PM
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Originally Posted by Skully View Post
If you wire the 2 that you have you will have 5megaohms. which is far from 500k ohms. You need brown black green resistors. And I would wire them like the second drawing, put a piece of heat shrink over top and seal them up.
brown black green got it. so i cover/shield all the way to the resistor or the entire thing? also if this doesnt work that would indicate that the connector to the ecu is the problem correct? what is that connector called? is it the sub harness?
thank you so much!!
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Old 05-27-2014, 01:09 PM
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Yup could be the knock sensor sub-harness as its called.

I would shield as much as you can.

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Old 05-27-2014, 01:16 PM
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Originally Posted by Skully View Post
Yup could be the knock sensor sub-harness as its called.

I would shield as much as you can.

i can tape the entire thing up ghetto style, i just wanna use this as a test. i will end up buying that top harness from z1, or maybe buy the bypass clip. but i like everything working properly so we shall see. when i replace the sub harness, do i just peel the insulation back and expect to find a clip, then clip the new on in, then the end that im jumping goes into the plug that is attached to the engine, that leads to the ks? or does that sub harness have to get routed all the way back to the ecu? i can probably look at the fsm but those diagrams are super tricky lmao

honestly though i thank you for your help i appriciate you guys! I'm so happy to have a z even if it is a beater slightly riced out and misfring all will be fixed soon.
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Old 05-27-2014, 01:21 PM
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Originally Posted by 97gtp View Post
i can tape the entire thing up ghetto style, i just wanna use this as a test. i will end up buying that top harness from z1, or maybe buy the bypass clip. but i like everything working properly so we shall see. when i replace the sub harness, do i just peel the insulation back and expect to find a clip, then clip the new on in, then the end that im jumping goes into the plug that is attached to the engine, that leads to the ks? or does that sub harness have to get routed all the way back to the ecu? i can probably look at the fsm but those diagrams are super tricky lmao

honestly though i thank you for your help i appriciate you guys! I'm so happy to have a z even if it is a beater slightly riced out and misfring all will be fixed soon.
Yeah the sub harness is only a short piece, it doesn't go all the way to the ecu. It plugs into the main harness, from there it goes to the ecu. For testing purposes just tape it up and check. It might be the harness, I was just reading up on old threads, and people have used one megaohm to test them, I was just going of what Nismo said. Either way, try the 500k as well.

Last edited by Skully; 05-27-2014 at 01:24 PM.
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Old 05-27-2014, 01:30 PM
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Here is a wonderfull writeup.

I would still recommend relocating the sensor. Up to you. Read and research.

http://www.zhome.com/ZCMnL/PICS/deto...ionSensor.html
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Old 05-27-2014, 01:48 PM
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Ok so this pack I bought only has brn black blue with gold as the fourth so how many would I need to make 500? All if them?? 5 in parallel
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Old 05-27-2014, 02:05 PM
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Nope, I would just get the brown black green and test it out.
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Old 05-27-2014, 02:33 PM
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Okay so still bad, I'm
Pretty sure it's the harness, now one last test I thought I heard of... Can I switch one of the other connectors and clip it on the ks clip? I thought I herd you can pull the vct ( the timing one which doesnt sound right) sensor or one of the other ones up top?
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Old 05-27-2014, 02:44 PM
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The connectors do interchange, but I do believe that the vct has no sub harness. And just make sure things ARE plugged in where they are suppose to be!! The white sheathing should be the VCT. Not plugged into the det sensor.

Last edited by Skully; 05-27-2014 at 02:48 PM.
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Old 05-27-2014, 07:14 PM
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thanks for all your help skully!
thanks to you to nismo!
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