Hey all, i've been trying to read up on what a knock sensor does for our car but pretty much of the threads i found were of code 52 or the wire breaking... what exactly does a knock sensor do besides detect knocks. Does the ecu use the vibrations to calculate any sort of data? i know i read that someone said when it detects a 7hz knock, thats when we get the code. But what i don't understand is how can the engine even run right if someone did the bypass mod. So say the ecu wasn't getting the knocksensor signal correctly, is it possible for the car not to run at its optimum, without even throwing a code?
knock sensors and what do they do
- Thread starter viper92086
- Start date
Knock sensor is there to protect the engine from knocking (pinging). If your engine is running and there is no knock, there is no need for it. It's a safety measure.
o ok, so it has absolutely nothing to do with performance of your motor, it only serves as saftey if something were to fail
JustAnotherVictim
Supramania Contributor
alright i was j/w, i'm doing the rewire tonight and was thinkin maybe the knock sensor had sumthing to do other than saftey
when you are pinging, the engine retards timing. It is to minimize detonation thus protecting the engine internally.
basically i wanan know is if the knock sensor is contstantly telling the ecu to adjust the timing, would have one with a loose connection reduce performance, meanwhile WITHOUT throwing a code?
JustAnotherVictim
Supramania Contributor
The knock sensor does "listen" for a 7 kHz frequency...this is the frequency that is produced when the engine experiences knock. However, this is not what produces a code 52. This code indicates a problem with the knock sensor circuit (open or short), the knock sensor itself, or the ECU.
When the ECU gets the signal that knock is occurring in one or more cylinders, it will retard timing. It bases the amount of retard on if the knock signal is "strong", "weak", or in between...basically it steps the amount of retard. When the knocking stops, the ECU restores timing advance a little at a time in fixed degrees.
When you have a code 52, the fail-safe function of the ECU sets ignition timing at a fixed retard angle (no more than 10 degrees iirc). This will definitely affect engine performance.
When the ECU gets the signal that knock is occurring in one or more cylinders, it will retard timing. It bases the amount of retard on if the knock signal is "strong", "weak", or in between...basically it steps the amount of retard. When the knocking stops, the ECU restores timing advance a little at a time in fixed degrees.
When you have a code 52, the fail-safe function of the ECU sets ignition timing at a fixed retard angle (no more than 10 degrees iirc). This will definitely affect engine performance.
Without going into detail the knock system is not passive but neither is it full time. The parameters needed to turn the system "on" are the same ones used to set the code ie; when the parameters are met the ECU begins knock control. If at that time it doesn't see the signal(s) used to monitor the sensor(s) and wiring it will set the code. Such use of shared programming for both control and diags is common in the TCCS.
Many knock sensors use an integral resistor to ground so the ECU can tricle some current through it to verify wiring. If you ohm a 7M sensor what do you get? Based on that one should ask oneself how the 7M ECU knows when the wiring is bad. The answer isn't hard to figure out if you think about it.
Many knock sensors use an integral resistor to ground so the ECU can tricle some current through it to verify wiring. If you ohm a 7M sensor what do you get? Based on that one should ask oneself how the 7M ECU knows when the wiring is bad. The answer isn't hard to figure out if you think about it.
i kinda understand how it works.. i was just wondering maybe my knocksensor wire could lead to my car not pulling as it should on some days... But keep in mind the light never came on until now.. so it was just a thought. Thanks guys, like i said i have the wire in front of me right now as i type this at work and i got the sogi how to so i'm set. i am going to be using the same sheilded thinnet wire as in the guide.
just out of curiosity is there any long term effects of code 52? since i am driving to canada in 1 week to road race i want to be able to make it back just in case this code haunts me... (NO i will NOT race if i am pulling code 52) thanks again
ATL88Supra said:
<-- runs a turbo charged engine without one single knock sensor
But I am standalone and so are the three other folks that I know that do not run a knock sensor.