Knock Sensor Self-Test
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Knock Sensor Self-Test
I've read about a pre-test the L98s ECM does when the engine is first started but I can't find the source of that info now.
As I recall it, when the engine is first cranked, the ECM sends a signal to the Knock Sensor and expects a return signal of a certain voltage. If the response isn't received, the ECM sets a code.
Diacom use to report those Knock Counts each time I started the engine. Also, a couple of other members recall reading the same self-test procedure but neither can recall where they read it.
I posted about the self-test on this on another Forum when I was trying to help a friend with his question but someone - who shall remain nameless, LOL - wants my source for the self-self test of the Knock Sensor system and I can't find the source.
I didn't find it in the 86 FSM, but I KNOW I read it somewhere. Just don't want guys to think I make up things. LOL
Does anyone know where I can find a source for the self-test that the ECM does on the system when the engine is first started?
Thanks,
Jake
As I recall it, when the engine is first cranked, the ECM sends a signal to the Knock Sensor and expects a return signal of a certain voltage. If the response isn't received, the ECM sets a code.
Diacom use to report those Knock Counts each time I started the engine. Also, a couple of other members recall reading the same self-test procedure but neither can recall where they read it.
I posted about the self-test on this on another Forum when I was trying to help a friend with his question but someone - who shall remain nameless, LOL - wants my source for the self-self test of the Knock Sensor system and I can't find the source.
I didn't find it in the 86 FSM, but I KNOW I read it somewhere. Just don't want guys to think I make up things. LOL
Does anyone know where I can find a source for the self-test that the ECM does on the system when the engine is first started?
Thanks,
Jake
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
Hi, I have Read about the ESC - Electronic Spark Control Module Self Test Recently.
It is outlined in my 1987 Factory GM Service Manual in the Driveability Section(s).
When the L-98 Car is started and driven, The ECM advances Ignition Timing to the Point where Engine Knock-Detonation takes place.
Detected by the Combination of the Block Mouted Knock Sensor to the ESC Knock Module and back the the ECM.
The ECM Retards Ignition Timing till Engine Knock is Detected No More.
ECM pulls a maximum of 20 Crankshaft Degrees Ignition Timing to Stop Engine Knock-Detonation.
Hope this Helps You Out.
BR
It is outlined in my 1987 Factory GM Service Manual in the Driveability Section(s).
When the L-98 Car is started and driven, The ECM advances Ignition Timing to the Point where Engine Knock-Detonation takes place.
Detected by the Combination of the Block Mouted Knock Sensor to the ESC Knock Module and back the the ECM.
The ECM Retards Ignition Timing till Engine Knock is Detected No More.
ECM pulls a maximum of 20 Crankshaft Degrees Ignition Timing to Stop Engine Knock-Detonation.
Hope this Helps You Out.
BR
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Joined: Apr 1999
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From: North Yorkshire, England
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Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
Jake, The last year for an external mounted ESC-Spark Knock Module was 1989 on a L-98 Powered Corvette.
In 1990 the Spark Knock Module was integrated into the PCM/ECM. And was kept Inside of the PCM/ECM up to 1996.
The 1990 ZR1 Corvette also used external mounted ESC-Spark Control Module.
BR
In 1990 the Spark Knock Module was integrated into the PCM/ECM. And was kept Inside of the PCM/ECM up to 1996.
The 1990 ZR1 Corvette also used external mounted ESC-Spark Control Module.
BR
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Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Me too. I cut my teeth on engines with their distributors at the rear of the block but since I've got two engines to maintain (mine and my son's 96) I didn't have much choice. Had to get up to speed on the up-front, Opti system or get left in the dust, LOL.
Jake
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Jake, The last year for an external mounted ESC-Spark Knock Module was 1989 on a L-98 Powered Corvette.
In 1990 the Spark Knock Module was integrated into the PCM/ECM. And was kept Inside of the PCM/ECM up to 1996.
The 1990 ZR1 Corvette also used external mounted ESC-Spark Control Module.BR
In 1990 the Spark Knock Module was integrated into the PCM/ECM. And was kept Inside of the PCM/ECM up to 1996.
The 1990 ZR1 Corvette also used external mounted ESC-Spark Control Module.BR
Jake
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
I have read here on Corvette Forum, searching older posts than the HOT setup for a LT-1 is to use and 1996 LT-4 ESC/Knock Module.
Its less sensitive to false knock counts created by long tube headers or roller tip rocker arms.
SUMMIT RACING IN OHIO still sells the upgrade LT-4 Knock module. Seen it a few weeks ago on their website.
I used their homepage search engine to find the LT-4 knock module
Remove Your PCM cover torx screws and install the new LT-4 Knock module.
I have not used this LT-4 knock Module myself.
My car is an 87 and take the externaly mounted ESC mounted by the heater box.
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
I am pretty sure Jake that the 90 and up Corvette's do a self test with the integrated-PCM located ESC/spark knock module.
I have read here on Corvette Forum, searching older posts than the HOT setup for a LT-1 is to use and 1996 LT-4 ESC/Knock Module.
Its less sensitive to false knock counts created by long tube headers or roller tip rocker arms.
SUMMIT RACING IN OHIO still sells the upgrade LT-4 Knock module. Seen it a few weeks ago on their website.
I used their homepage search engine to find the LT-4 knock module
Remove Your PCM cover torx screws and install the new LT-4 Knock module.
I have not used this LT-4 knock Module myself.
My car is an 87 and take the externaly mounted ESC mounted by the heater box.
I have read here on Corvette Forum, searching older posts than the HOT setup for a LT-1 is to use and 1996 LT-4 ESC/Knock Module.
Its less sensitive to false knock counts created by long tube headers or roller tip rocker arms.
SUMMIT RACING IN OHIO still sells the upgrade LT-4 Knock module. Seen it a few weeks ago on their website.
I used their homepage search engine to find the LT-4 knock module
Remove Your PCM cover torx screws and install the new LT-4 Knock module.
I have not used this LT-4 knock Module myself.
My car is an 87 and take the externaly mounted ESC mounted by the heater box.
What I'm interested in knowing is about the self-test procedure. Specifically, does the LT system still do it.
Jake
