knock sensor question
 

does anyone know how the stock ECU knows that the knock sensor is connected? that may sound like a stupid question that could be answered by "if it's plugged in!!!" but i'm wondering what resistance or frequency it needs to see to determine that it is functioning.

I am basically wondering this because i would like to over-ride it and trick the stock ECU into thinking that it's there. not because i don't like the idea of the knock sensor, but because i can't afford to buy a new knock sensor... so PLEASE, people, don't give me the "omg bro just buy a used knock sensor omg."

I am simply curious, and I would like to remove this sensor and trick the ECU like i did with the emissions solenoids.

also, i am fairly well versed in the FSM, and this information is not in the FSM.


cliff notes:
Does the stock ECU see the knock sensor by resistance or by frequency?

beuller...

Resistance of mine at about 50F is 580K ohms.

That sounds about right IIRC. You can set the resistance to give a voltage of about 5 to 6 volts DC at the sensor lead (as referenced to ground), you'll be okay. This is used to verify the presence of the sensor and serves as a bias voltage as well.

thanks for the info.

any idea what ohm/watt resistor i would need to do this?

The power consumption is going to be miniscule for a resistor of this rating so a standard colour-banded resistor (usually rated at 1/4W) should work. A 600k ohm resistor will probably be within range (unless you can find a 580k ohm one).

ok great info thanks.

i will post up results after i hit up radioshack tomorrow :)

i couldn't find any 600k ohm resistors.

i was thinking maybe you meant to type 600ohm? i got an assortment of 1/4 watt and 1/2 watt resistors, but i'm not exactly sure which one(s) to use (or which resistance range the ECU needs to see)

Definitely 580k ohms. You might not find exactly 600 k ohms but mouser.com have 560k ohm and 600k ohm metal film resistors (the small colour-coded types).

In the Bay Area we have Frys (think Radio Shack x 100) so I have not been to Radio Shack in years and do not know what their selection is like.

radio shack didn't have anything over 30k ohms.

can't i up the wattage and use a lower ohm resistor? I'm not exactly sure how this works. i may have it backwards.

Definitely not. The ECU needs to see 600k ohms or so - or it will throw a code.

I know you don't want to hear this, but I'd pick up a knock sensor in the classifieds.

Wattage rating is not critical for that application (other than they may cost a little more). You could use a higher wattage resistor if that is all you can find. You could also combine different value resistors to get close to 580k ohms: two 290k resistors wired in series (end to end) add to 580k ohms; or two 1.2M ohm resistors connected in parallel would give a value of 600k. But I agree with others, it is not a good idea to eliminate the knock sensor.

ok guys thanks for the info. i'll try to wire a few in series to up the resistance to to 580k ohms

update: i connected two 1M ohm resistors in parallel, and one 100k ohm resistor at the end of those, and grounded one end, which would result in 600k ohms... well it didn't work and the CEL is still on.

Get a real knock sensor? There is absolutely no reason to remove it.

thewird

thewird, you wanna buy me one?

http://ohnolookoutitsaraygun.com/argh-Picard.jpg

thewird

https://www.rx7club.com/forum/attach...8&d=1230509555



jacobcartmill

^
https://www.rx7club.com/attachment.p...1&d=1230511165