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Discussion Starter #41
Exactly what is it that you are calling the "ignition module"?
I have no idea lol

In researching, many articles are saying to check plugs, then coils, then ignition module. All I can find is that it's built into the throttle body on these.

Idk what it is or what it does to tell you the truth lol
 

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2002 chevy trailblazer_lt
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There is no such thing built into these throttle bodies!!

The coils themselves handle the making of the spark and these coils are controlled by the PCM (powertrain controller module). That's the thing bolted to the intake manifold near the brake fluid reservoir. There are no other modules involved with this.

I myself am real old school mechanic trained in the early 70s before there were these fancy modules and just now is the first time I have had a look at our new fangled coils!! I just did a fun experiment, at least I had fun with it! Check this out....

 

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Discussion Starter #43
There is no such thing built into these throttle bodies!!

The coils themselves handle the making of the spark and these coils are controlled by the PCM (powertrain controller module). That's the thing bolted to the intake manifold near the brake fluid reservoir. There are no other modules involved with this.

I myself am real old school mechanic trained in the early 70s before there were these fancy modules and just now is the first time I have had a look at our new fangled coils!! I just did a fun experiment, at least I had fun with it! Check this out....

I need to do that exact test lol

No idea how to hook all of that up though

I would much prefer testing them like that than cranking my engine over
 

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I do note one odd thing about your multimeter measurements of the coil terminals. Terminal C is the closest one to the bolt that secures the coil. That terminal is ground, the black wire(s). On all of mine as I would expect, there is little or no resistance to the metal of the coil. You listed no readings of zero resistance. Did you now measure in this way?

PXL_20210403_222543367.jpg
 

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Discussion Starter #45
I do note one odd thing about your multimeter measurements of the coil terminals. Terminal C is the closest one to the bolt that secures the coil. That terminal is ground, the black wire(s). On all of mine as I would expect, there is little or no resistance to the metal of the coil. You listed no readings of zero resistance. Did you now measure in this way?

View attachment 56846
I did what you're doing, I just used leads instead of the clamps going to the leads.
I ran the red lead to each pin and the black lead to the brass (in your pic, silver) band around the coil.
 

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Discussion Starter #46
I did what you're doing, I just used leads instead of the clamps going to the leads.
I ran the red lead to each pin and the black lead to the brass (in your pic, silver) band around the coil.
it does report zero, but it flashes a number first. The number it flashed is the number I logged.... It flashes for half a second and then reports zero
 

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Discussion Starter #47
it does report zero, but it flashes a number first. The number it flashed is the number I logged.... It flashes for half a second and then reports zero
I followed this test... You'll see what I'm talking about with the number flashing.


I only logged the number to compare them.
 

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Discussion Starter #48
I followed this test... You'll see what I'm talking about with the number flashing.


I only logged the number to compare them.
I have a test light with an alligator clip....I wonder if I connected that alligator clip to positive battery terminal and I grounded the plug and the coil, if I could then use the test light as a substitute to fire the coil without turning then engine over and see if the plug sparks.

Think that would work?
 

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For the coil to spark it needs these things...

A) 12 VDC power to terminal A, where the pink wire would normally connect. This is the terminal furthest away from the bolt that secures the coil.
B) A connection to either frame ground or negative battery terminal to any of these 3 places which are all connected together inside the coil... Terminal C where the black wire normally connects, the finned top of the coil, or the metal piece wrapping the coil body. Any of these three locations will provide the proper ground to the coil.
C) 12 VDC signal power to terminal B, the center of the three harness connector pins. Your test light idea from battery lositive just might do this part.

When those three connections are preaent the coil activates but you also need somewhere for the spark to go. Best case is to use a spark plug and you then must ground the threaded part of the spark plug, us8ng the same sort of ground source as terminal C, either frame ground or battery negative.
 

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Discussion Starter #50
For the coil to spark it needs these things...

A) 12 VDC power to terminal A, where the pink wire would normally connect. This is the terminal furthest away from the bolt that secures the coil.
B) A connection to either frame ground or negative battery terminal to any of these 3 places which are all connected together inside the coil... Terminal C where the black wire normally connects, the finned top of the coil, or the metal piece wrapping the coil body. Any of these three locations will provide the proper ground to the coil.
C) 12 VDC signal power to terminal B, the center of the three harness connector pins. Your test light idea from battery lositive just might do this part.

When those three connections are preaent the coil activates but you also need somewhere for the spark to go. Best case is to use a spark plug and you then must ground the threaded part of the spark plug, us8ng the same sort of ground source as terminal C, either frame ground or battery negative.
well, I hooked up the newest coil to the actual harness and turned it over with a plug in and the plug sparked. Twisted with the same coil pack and all 6 plugs fired.

Chose one plug that was sparking and used it to test the other 5 coil packs in the same way and NONE of them sparked.

In that test, I have one good coil and need to replace 5
 

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When you tested the 5 coil packs with the known-to-spark plug,,, did you test each coil on the very same harness connector so the only variable was the coils themselves?
 

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Discussion Starter #52
When you tested the 5 coil packs with the known-to-spark plug,,, did you test each coil on the very same harness connector so the only variable was the coils themselves?
yep.... Same harness, same plug. Started with known good coil & it sparked the plug, the next 5 didn't, then tested known good coil once again and it sparked.

now, I'm wondering what would make 5 coils go bad at once
 

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That is mind boggling indeed!! Do you know if any of them were originals? My 2002 TrailBlazer has 284xxx miles on it and 4 of the coils are original! I have had two failures while driving and luckily for me the second one happened in the middle of nowhere, northeastern New Mexico but I had a new spare with me and just the minimum tools to swap it!

The coil in my video recently came from a junkyard for $12 as a spare to keep handy. I see a lot of owners on the Facebook groups using the inexpensive sets of 6 from Amazon but I think they have a higher failure rate maybe.
 

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Discussion Starter #54
That is mind boggling indeed!! Do you know if any of them were originals? My 2002 TrailBlazer has 284xxx miles on it and 4 of the coils are original! I have had two failures while driving and luckily for me the second one happened in the middle of nowhere, northeastern New Mexico but I had a new spare with me and just the minimum tools to swap it!

The coil in my video recently came from a junkyard for $12 as a spare to keep handy. I see a lot of owners on the Facebook groups using the inexpensive sets of 6 from Amazon but I think they have a higher failure rate maybe.
I'm not sure... They've been in it as long as I've had it. I've only ever had to change the one.
I'm just hoping there's not an issue causing them to go bad that's just gonna continue to cause them to go bad.

Great news about the cheap ones from Amazon because I just ordered them lol

I just wanna make sure that fixes my problems before I invest in the more expensive ones
 

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About the only thing I could think might affect all coils would be power supply/ground issues. It might be wise to go ahead and get at that ground on the side of the engine and clean that up.

I did notice something when testing the resistance of my coils. The original ones have a much lower resistance from the power terminal A to ground than the newer replacement coils do. That means the older ones will draw more amperage than the newer ones.
 

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Discussion Starter #56
About the only thing I could think might affect all coils would be power supply/ground issues. It might be wise to go ahead and get at that ground on the side of the engine and clean that up.

I did notice something when testing the resistance of my coils. The original ones have a much lower resistance from the power terminal A to ground than the newer replacement coils do. That means the older ones will draw more amperage than the newer ones.
coils should be here Wednesday... Doubt I'll do much to it tomorrow.
If I do, I'll keep you posted.

Hope you and your family have a great Easter, man
 

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Check the fuse box under the hood. It could have a bad electrical connection that would cause the problem you have. I had a similar problem and replacing the fuse box fixed it.
 

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I'm not sure... They've been in it as long as I've had it. I've only ever had to change the one.
I'm just hoping there's not an issue causing them to go bad that's just gonna continue to cause them to go bad.

Great news about the cheap ones from Amazon because I just ordered them lol

I just wanna make sure that fixes my problems before I invest in the more expensive ones
I changed out my coils nearly a year ago with a cheap set of coils (less than $60 from ebay) and a new set of delco plugs. My '02 TB EXT had 180,000 +/- on it and two coils went down at the same time and made it run very weak and start drinking fuel like a drunk sailor loves his whiskey. I've put nearly 20,000 miles on the cheap ones, and have had no issues with them at all. I kept the 4 used ones that were good and put them in the compartment in the floor above the spare tire just in case I did have an issue while on the road.
 

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My 2002 TrailBlazer has 284xxx miles on it and 4 of the coils are original!
Sir, you are definately on borrowed time with those original coils! You have been blessed to get far more time from them than they were engineered to give!
 
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