Knock sensor....
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
Knock sensor....
I've finally got the car under control mechanically, and electrically... for the most part... I wanna start modding, but not before it's running perfect... anyway-
I get a code 43 very intermittant... I'm assuming it's retarding my timing, because I seem to lose power when it shows up.
I do not hear knocking or pinging. The engine sounds perfectly normal... cleaned the sensor and the electical connection going to it...
What happens if you just disconnect the knock sensor?
I get a code 43 very intermittant... I'm assuming it's retarding my timing, because I seem to lose power when it shows up.
I do not hear knocking or pinging. The engine sounds perfectly normal... cleaned the sensor and the electical connection going to it...
What happens if you just disconnect the knock sensor?
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by 6spd
thats not wise to do. you could have a bad senser or false knock. if you disconnect the wire i think the car will go into limp mode. whats your timing set at??
-JRC-
Team Owner
Joined: Sep 2003
Posts: 20,170
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by 6spd
disconnect battary and hook it back up
We got tired of constantly pulling the cable and installed this beauty for just that purpose.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by mikey whipreck
okay... .but does anyone have any
suggestions for my question?
suggestions for my question?
counts. Do this by creating a situation where is CAN'T knock,
and monitor for counts. In my case I got counts, revving it in neutral,
with a load of 91 octane gas (best we can get here) and the base
timing set to zero. There is no way a 9:1 engine can be ping under
those conditions. As a result, I have disconnected my knock sensor
and I rely on my ears to detect knock, just like the good old days.
Other cures are, actually finding and eliminating the source of the noise
causing the false counts, and/or changing to a better ESC module as
outlined it the Tech Tips section.
If the counts are TRUE knock, you need to find the cause and
eliminate that.
That will get you started (finished?)
RACE ON!!!
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Le Mans Master
Joined: Jul 2002
Posts: 5,818
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From: Alive and well in Burlington NC
The operation of the knock sensor should be transparent. It will sense detonation before you can hear it and pull timing accordingly to prevent engine damage. When you get a code 43, the ecm is seeing a problem with either the sensor or the circuit.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Once after each start up the ECM advances timing, within limits, till it gets a knock count; if it doesn't get a knock count during this test it will set the code and go into limp home mode to protect the engine.
Your problem is due to a problem in the knock detection circuit that should be corrected. This can be due to a wiring problem, or a faulty knock sensor or, on '85-'89 L98s, a faulty ESC module.
As a first step verify that the connector hasn't fallen off the knock sensor.
What year car do you have???
BTW, to reset from limp home mode, just turn the engine off and restart it. It shouldn't recheck the knock sensor till after you are on the highway again.
The easiest way to reset trouble codes with an OBD-I system is to open the connector in the single Orn wire comming off the battery + terminal. This removes power only from the ECM so you can reset codes without losing all your other presets.
Your problem is due to a problem in the knock detection circuit that should be corrected. This can be due to a wiring problem, or a faulty knock sensor or, on '85-'89 L98s, a faulty ESC module.
As a first step verify that the connector hasn't fallen off the knock sensor.
What year car do you have???
BTW, to reset from limp home mode, just turn the engine off and restart it. It shouldn't recheck the knock sensor till after you are on the highway again.
The easiest way to reset trouble codes with an OBD-I system is to open the connector in the single Orn wire comming off the battery + terminal. This removes power only from the ECM so you can reset codes without losing all your other presets.
Last edited by 65Z01; Oct 24, 2004 at 04:55 PM.
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
to answer some questions-
Mine's an 85, i recently removed the knock sensor cleaned it and cleaned the electrical connections and reconnected the thing, my book points to the knock sensor as being next to the starter on the passenger side, pull the sensor and watch the coolant flow- just to make sure I have the right sensor...
I'm not really quite sure what 'limp home mode' is, but that's not really important..
So see if I understand the replacement procedure. the only things that can set off a code 43, are the sensor itself, the ESC, or the wiring between, correct? Are there any points in the wiring I need to look for?
What would you recommend I replace first?
Mine's an 85, i recently removed the knock sensor cleaned it and cleaned the electrical connections and reconnected the thing, my book points to the knock sensor as being next to the starter on the passenger side, pull the sensor and watch the coolant flow- just to make sure I have the right sensor...
I'm not really quite sure what 'limp home mode' is, but that's not really important..
So see if I understand the replacement procedure. the only things that can set off a code 43, are the sensor itself, the ESC, or the wiring between, correct? Are there any points in the wiring I need to look for?
What would you recommend I replace first?
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
Originally Posted by 6spd
well if your car goes into limp mode your car will run like a bag of *** so it is important. it's like a safty mode
I meant that i've never experienced this, so it's not imperative to my immediate question...
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
The big question is did you have this problem before you pulled and cleaned the knock sensor???
If not look to the work you did on it as the cause of the problem. So check the integrity of the connecton to the knock sensor. if it it ok, check the ECM/IGN fuse; if ok, proceed below.
With the engine idling test voltage on the Blk wire from the ESC module and verify it is under 6Vdc; if not there is a faulty connection to ECM B7.
If under 6Vdc stop the engine and again check the voltage on the Blk wire; if over 6Vdc replace the ESC module (see my site for P/N).
You can test the knock sensor by rapping on the exhaust manifold or the block near the sensor to see if a signal is detected on the Blk wire from the ESC module.
And, yes, it does sound as though you indeed pulled the knock sensor as it penetrates into the coolant.
BTW, the ECM tests the knock sensor when the engine is under load, such as at WOT, and coolant temp is over 205deg F.
If not look to the work you did on it as the cause of the problem. So check the integrity of the connecton to the knock sensor. if it it ok, check the ECM/IGN fuse; if ok, proceed below.
With the engine idling test voltage on the Blk wire from the ESC module and verify it is under 6Vdc; if not there is a faulty connection to ECM B7.
If under 6Vdc stop the engine and again check the voltage on the Blk wire; if over 6Vdc replace the ESC module (see my site for P/N).
You can test the knock sensor by rapping on the exhaust manifold or the block near the sensor to see if a signal is detected on the Blk wire from the ESC module.
And, yes, it does sound as though you indeed pulled the knock sensor as it penetrates into the coolant.
BTW, the ECM tests the knock sensor when the engine is under load, such as at WOT, and coolant temp is over 205deg F.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by mikey whipreck
okay... .but does anyone have any suggestions for my question?
Racer
Joined: Sep 2004
Posts: 323
Likes: 1
From: Muncie Indiana
Just a thought
If you want to you can check my thread of last week called Service Engine Soon light.
In there I point out that I have begin to isolate my light to the place I normally buy gas. If I am on the road or buy locally at another station I have never had the light only at one station.
I believe the sensor is doing just what it is supposed to do. It is telling me that for some reason it's not happy with the gas from that station. 
In there I point out that I have begin to isolate my light to the place I normally buy gas. If I am on the road or buy locally at another station I have never had the light only at one station.
I believe the sensor is doing just what it is supposed to do. It is telling me that for some reason it's not happy with the gas from that station.
Thread Starter
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
Originally Posted by 65Z01
The big question is did you have this problem before you pulled and cleaned the knock sensor???
Originally Posted by 65Z01
BTW, the ECM tests the knock sensor when the engine is under load, such as at WOT, and coolant temp is over 205deg F.
Originally Posted by CFI-EFI
First check for false knock
counts.
counts.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by 65Z01
False knock isn't the problem here, as it's presence does not cause the ECM to throw the code; only a failure on the knock test by the ECM will cause the code.
RACE ON!!!