Ignition module ? on a '97 Blazer
Thread Starter
Team Owner
Joined: Aug 2004
Posts: 22,285
Likes: 207
From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
Ignition module ? on a '97 Blazer
Thought I'd ask here, as I'm having no luck anywhere else.
The Ignition module crapped out on the wife yesterday.
I ran down the list of possibles before I determined it was the Ign. module. Fuel pump primed at switch to on position. Put a timing light on the #1 plug wire, no spark. Checked input voltage to coil, it was at 12V. Checked coil output wire to block, plenty of spark.
Went to Napa, got an Echlin unit, replaced the module, the truck fired right up. Idled fine.
Took it for a 6 mile jaunt, and the thing misses like crazy at normal accelleration, and during cruising speeds. If I hammer the throttle, it runs great, no misses.
On the return trip home, Service Engine Soon light came on, P0300 - Random/Multiple misses.
Now, the truck ran fine until it just stopped mid-trip on the wife.
So, can it be a deffective module?
It doesn't smell like raw gas, so I don't think the injector spider setup took a magical dump.
The Ignition module crapped out on the wife yesterday.
I ran down the list of possibles before I determined it was the Ign. module. Fuel pump primed at switch to on position. Put a timing light on the #1 plug wire, no spark. Checked input voltage to coil, it was at 12V. Checked coil output wire to block, plenty of spark.
Went to Napa, got an Echlin unit, replaced the module, the truck fired right up. Idled fine.
Took it for a 6 mile jaunt, and the thing misses like crazy at normal accelleration, and during cruising speeds. If I hammer the throttle, it runs great, no misses.
On the return trip home, Service Engine Soon light came on, P0300 - Random/Multiple misses.
Now, the truck ran fine until it just stopped mid-trip on the wife.
So, can it be a deffective module?
It doesn't smell like raw gas, so I don't think the injector spider setup took a magical dump.
Safety Car
Joined: Oct 2007
Posts: 3,816
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From: :45 minutes from everywhere / E-I-E-I-O
Yup. That's the symptom my '94 has goin' on right now - H41 ICC open circuit (module in the circuit), only when warmed up.
Some other poster here [Redeasy?] said the parts retailers Advance / Zone will test the module. That was a good tip. Mine passed. I'm waitin' for new wires, since one was questionable, AND, since the dealer serv manager said it could be the problem.
Otherwise, I'll have to pull the harness and wire in a by-pass for each link in ICC circuit. I've got Chilton's
for S-Series if you don't have it. Not much in them, but you never know... I do '98 Jimmy.
Some other poster here [Redeasy?] said the parts retailers Advance / Zone will test the module. That was a good tip. Mine passed. I'm waitin' for new wires, since one was questionable, AND, since the dealer serv manager said it could be the problem.
Otherwise, I'll have to pull the harness and wire in a by-pass for each link in ICC circuit. I've got Chilton's
for S-Series if you don't have it. Not much in them, but you never know... I do '98 Jimmy.
Thread Starter
Team Owner
Joined: Aug 2004
Posts: 22,285
Likes: 207
From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
I have a code reader that erases codes, but it doesn't rest the ECM.
Thread Starter
Team Owner
Joined: Aug 2004
Posts: 22,285
Likes: 207
From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
Yup. That's the symptom my '94 has goin' on right now - H41 ICC open circuit (module in the circuit), only when warmed up.
Some other poster here [Redeasy?] said the parts retailers Advance / Zone will test the module. That was a good tip. Mine passed. I'm waitin' for new wires, since one was questionable, AND, since the dealer serv manager said it could be the problem.
Otherwise, I'll have to pull the harness and wire in a by-pass for each link in ICC circuit. I've got Chilton's for S-Series if you don't have it. Not much in them, but you never know... I do '98 Jimmy.
Some other poster here [Redeasy?] said the parts retailers Advance / Zone will test the module. That was a good tip. Mine passed. I'm waitin' for new wires, since one was questionable, AND, since the dealer serv manager said it could be the problem.
Otherwise, I'll have to pull the harness and wire in a by-pass for each link in ICC circuit. I've got Chilton's
for S-Series if you don't have it. Not much in them, but you never know... I do '98 Jimmy.My understanding is, they excite the internal circuits, to either open or close. No load, or heat stress applied. The unit could pass on the test, and fail in the field.
BTW, During the 12 mile trip I made, I stopped at a shop for 3.5 hours.
After letting the truck sit for 2.5 hours, I went out and checked all the connections, and when I felt the heat sink the module is on, the sucker was quite warm yet, I'd say over 125 degrees (just guessing, but it was hot).
Thread Starter
Team Owner
Joined: Aug 2004
Posts: 22,285
Likes: 207
From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
Yup. That's the symptom my '94 has goin' on right now - H41 ICC open circuit (module in the circuit), only when warmed up.
Some other poster here [Redeasy?] said the parts retailers Advance / Zone will test the module. That was a good tip. Mine passed. I'm waitin' for new wires, since one was questionable, AND, since the dealer serv manager said it could be the problem.
Otherwise, I'll have to pull the harness and wire in a by-pass for each link in ICC circuit. I've got Chilton's for S-Series if you don't have it. Not much in them, but you never know... I do '98 Jimmy.
Some other poster here [Redeasy?] said the parts retailers Advance / Zone will test the module. That was a good tip. Mine passed. I'm waitin' for new wires, since one was questionable, AND, since the dealer serv manager said it could be the problem.
Otherwise, I'll have to pull the harness and wire in a by-pass for each link in ICC circuit. I've got Chilton's
for S-Series if you don't have it. Not much in them, but you never know... I do '98 Jimmy.My understanding is, they excite the internal circuits, to either open or close. No load, or heat stress applied. The unit could pass on the test, and fail in the field.
BTW, During the 12 mile trip I made, I stopped at a shop for 3.5 hours.
After letting the truck sit for 2.5 hours, I went out and checked all the connections, and when I felt the heat sink the module is on, the sucker was quite warm yet, I'd say over 125 degrees (just guessing, but it was hot).
Well, anyway, I'm heading over to Napa in an hour or so, with the module.
I doubt they'll replace it, the guy will probably send it to a sister shop for testing.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Assuming it's a 4.3 Liter, I'd be more inclined to suspect the injectors or spiders. Covered under a Special, 200K warranty in CA (to avoid a recall). Cleaning clears the 300 and the driveability issue - on the Dealer out here.
Thread Starter
Team Owner
Joined: Aug 2004
Posts: 22,285
Likes: 207
From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
Went in to Napa.
The guy's gonna get me an A.C.Delco unit, but it'll take till tomorrow to get it.
Took the Echlin unit back home, installed it, and guess what?
No spark to any plugs. Plenty of juice at the coil.
(Read above about the 2.5 hour heat test)
The damn thing is toasted.
Has to be a bad unit from the start.
First time (in 39 years) I've every got a crappy part from a name brand house.
The guy's gonna get me an A.C.Delco unit, but it'll take till tomorrow to get it.
Took the Echlin unit back home, installed it, and guess what?
No spark to any plugs. Plenty of juice at the coil.
(Read above about the 2.5 hour heat test)
The damn thing is toasted.
Has to be a bad unit from the start.
First time (in 39 years) I've every got a crappy part from a name brand house.
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Thread Starter
Team Owner
Joined: Aug 2004
Posts: 22,285
Likes: 207
From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
Not available here, I presume. (I never got notice of it, I'm the original owner, 66K miles)
Safety Car
Joined: Oct 2007
Posts: 3,816
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From: :45 minutes from everywhere / E-I-E-I-O
If it tested good, it might be good. BUT, if it tested BAD, I'd probably put $$$ on it really is bad. Just like carfax - clean means no hits = ??? But hits on a carfax is probably more reliable............
Team Owner
Joined: Oct 2000
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From: Fort Knox, KY
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First time (in 39 years) I've every got a crappy part from a name brand house.
It's becoming more and more common as parts get outsourced to India, China, Mexico, etc...
It's becoming more and more common as parts get outsourced to India, China, Mexico, etc...
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
I believe it's Bulletin C99066E - '96 to 2001, 4.3, 5.0 and 5.7 motors (CA only). Looking at the letter, the warranty was 10/200. My truck is gone, so I no longer worry about it - but the one time it happened, it was on the Dealer and they patched it back up with whatever wonderous device they have to clean it out. I mention it because a bad ignition module is rare, and if the original poster can't resolve it, he might try the S-10 forum (if it's still up).
