I have a 1986 base, and got a spark control module code. I replaced the module, erased the code, and 2 days later, I have the same code. I have erased the code twice now, once by disconnecting the batterey, and once by pulling the SCM fuse, but it continues to pop back up. Am I doing something wrong, or am I missing something?

 

Please help!

 

Which fuse is the SCM fuse? I assume you mean the ECM/IGN fuse. This does NOT clear the error codes.

The ECM does not have a fuse. It uses a fusible link at the positive battery terminal. There is a connector there that you can use to reset the error codes. Opening the connector for about 1 second will erase all the error codes (and cause all the BLMs to be reset to 120).



I assume you're talking about error code 43. There are two ways to get this error code (they should have given them two different numbers, but we're stuck with the way it is). When the engine is first started, the ECM advances the spark by 20° and looks for knocks being reported by the ESC module. If it does not see at least 2 knocks it sets error code 43. The way to test for this is to clear the error codes and start the engine. Check for error codes and if you see 43 then something is wrong with the knock circuit because it is not reporting knocks.

The second way to get error code 43 is when the ESC senses knocks while driving. In that case the ECM will retard the spark as an attempt to stop the knocking. The ECM will set error code 43 if it sees the following conditions:

RPM > 650
MPH > 2
Coolant temperature > 194°F (90°C)
Electronic Spark Control voltage < 6 volts on ECM pin B7 <-- that means that knocks are being detected
All above conditions must be met for > 4 seconds

 

Yes, my scan tool said removing that fuse would erase the code...it did nothing, I also disconnected the negative cable..Not sure it did anything to the code. I will follow your instructions to erase the code. I have had no runability problems after replacing the ESCM, but before I replaced it, I had a couple instances of the car not staying running after start up, and sounding like it was not firing on all cyliders when cold. Once I started moving the car, these issues disappered.

Now, when I start the car and go for a drive, the code 43 pops the light on after a couple of miles. Once the car is warm, and I shut it off, everytime I re-start the car, regardless of how far I drive, the light does not come back on. Once it is cold again, and I start the car and go for a drive, after a couple miles the light comes on again.

I have made sure the wires are routed correctly, and all of my brackets are tight. My PCV valve is certainly operating, it almost sounds like it is rattling it moves in and out so frequently during idle. Due to position and time constraints to date, I have not looked at the EGR or knock detector.

I appreciate the information, will clear the code and keep you posted. Much appreciation!

 

OK, so I erased the code per instructions, drove the car 3 times today. The third trip was the longest, about 7 miles. After 6 miles, check engine light came on again. Checked the code, 43 again. Which direction do I take from here?

 

The only way to find out what is really happening is to get an ALDL cable and datalog with a laptop.

 

Well, I have a scan tool that gives live streaming data. What should I be looking for?

 

Look for anything that looks weird.

That's why a data logging program can be so useful. What I have done is import the data log into Excel. Then you can scroll through the data and see where things go wacko. I have also graphed various parameters to see how they changed over time.

 

Hi, I am new here and dont even no if i am doing this in the right place? Sorry if I'm not, (its a blonde thing!) but ill figure it out soon I promise!

Back to the ESCM problems- I have an 85 coupe and had some engine problems- it started what I call loping. When I was at idle, it would almost die, fine all other gears, so I thought it was idle control - anyway getting to the point I also kept receiving code 43 and when it became so bad I couldnt even get it started I replaced it-(ESCM)She
ran absolutely perfect - about 5 days started again- I replaced again then scan said same and I followed that on down to knock sensor -which made sense because of problems with my radiator anyway replaced that and still starting to lope?
I read this morning about clearing codes completley so I just went out and did that and now I'm gonna take her out, come home see what codes I come up with-
My problem is not the light coming on mine effecting my engine performance - and not running correct and have followed almost everything i have found on it.
Could it be a short in my electrical wires somewhere that is making a sort of domino affect with my sensors etc? One shorting making all others read and run incorrectly? Thats the feel im getting sometimes?
Im no mechanic and no my limits but have had 5 corvettes- and done almost everything I can myself I love working on her! So I know a lil bit.
I hate it when my girl is sick!!! She has been good runner considering what she has went thru and never left me stranded and I try to keep her in best shape possible for 30 yo she is running and looking good!
I am very glad I finally found this place, nice to be here and meet everyone.
I so hope i am putting this in right place LOL
Going for a spin, get new codes!!!!

 

You really should start a new thread. As it is, the answers to your problem and the original problem will get mixed together and confuse everybody. What you have done is known as hijacking a thread and is considered rude netiquette.

 

That is exactly why I said I hope I'm doing this in the right place,
please forgive me I am new and have not figured it out. I am very sorry not trying to hijack anything just trying to find help

 

So I replaced my ESCM, knock sensor and then my EGR valve and the problems went away. It idles smooth, has more pull, and the stupid light no longer comes on. Plus, it is a cheap fix. (I also replaced a cracked vacuum line.)

The next day I drove it to college...I am a 45 y.o. student...again, and when I came out to go home at 9:20 P.M. the car would not start. But, fear not, the previos owner stripped out the negative battery cable connection. So a couple minutes later, I was on my way home. Hope that helps - have a great day. Plus, have to say thanks again for the info - you pointed me in the right direction and I appreciate the assist.