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Bad ICM? 3800 by Threedog
Started on: 05-26-2015 09:39 PM
Replies: 19 (261 views)
Last post by: phonedawgz on 05-28-2015 03:25 PM
Threedog
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Report this Post05-26-2015 09:39 PM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
Crank/no start. Getting 12v at pin P of the ICM connector(drops to 10v during crank) but I dont get a spark on any wires. Engine was working perfectly before the swap. ICM harness checked out as good. ICM grounded through the harness and the back plate(is that needed?). ECM has not thrown any codes.

Is this just a bad ICM?
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Mike Gonzalez
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Report this Post05-26-2015 11:12 PM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is this a new swap? Did you buy or build your harness? Was you PCM reprogreammed? Are all your fuses good? Do you get a Check engine light during bulb test when you turn the key on? Do you have power to the PCM at pins C1-19 and 20 with the key on?
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phonedawgz
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Report this Post05-27-2015 03:36 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Bad wiring to the crank sensor? Bad crank sensor?
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Threedog
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Report this Post05-27-2015 05:50 AM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike Gonzalez:

Is this a new swap? Did you buy or build your harness? Was you PCM reprogreammed? Are all your fuses good? Do you get a Check engine light during bulb test when you turn the key on? Do you have power to the PCM at pins C1-19 and 20 with the key on?


Yes, build, yes(Sinister), yes, yes, didnt check. How would the ECM make a connection to an OBD2 sensor if 19/20 didnt have power?
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Threedog
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Report this Post05-27-2015 05:51 AM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post

Threedog

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quote
Originally posted by phonedawgz:

Bad wiring to the crank sensor? Bad crank sensor?


This was my worry. How do I test a crank sensor though? Is it really likely to fail right durning my swap?
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Mike Gonzalez
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Report this Post05-27-2015 08:39 AM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
Crank sensor was going to be my next suggestion to if everything else checked out. But if you tested it and it was good, i cant imagine it just failing.
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Threedog
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Report this Post05-27-2015 08:55 AM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike Gonzalez:

Crank sensor was going to be my next suggestion to if everything else checked out. But if you tested it and it was good, i cant imagine it just failing.


Yeah engine was running fine right before swap (really well actually). Thinking about it, I accidentally swapped battery connectors (neg for pos) without the computer plugged in. Could that have fried the icm?
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Mike Gonzalez
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Report this Post05-27-2015 09:52 AM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
I suppose its possible, but I doubt it. I have done that a couple times without damaging anything. You can usually take your ICM to the parts store for free testing.
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Threedog
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Report this Post05-27-2015 10:44 AM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike Gonzalez:

I suppose its possible, but I doubt it. I have done that a couple times without damaging anything. You can usually take your ICM to the parts store for free testing.


Both O'Reillys and Autozone said they dont do it..
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Threedog
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Report this Post05-27-2015 10:47 AM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post

Threedog

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Just to be clear, the ICM is the flat unit that the coil packs attach to and has the thin long connector, correct?
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Mike Gonzalez
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Report this Post05-27-2015 10:50 AM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well that blows, Autozone still tests them here. Yes thats the ICM
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Threedog
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Report this Post05-27-2015 11:20 AM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike Gonzalez:

Well that blows, Autozone still tests them here. Yes thats the ICM


Does a bad icm mean bad coil packs? Or can I reuse them?
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Mike Gonzalez
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Report this Post05-27-2015 12:27 PM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
You can typically reuse them
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Mike Gonzalez
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Report this Post05-27-2015 01:05 PM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
If it was running fine before i would go through double checking all the basics before replacing the ICM, make sure your engine and chassis is grounded well along with what i listed earlier.
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Threedog
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Report this Post05-27-2015 01:56 PM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Mike Gonzalez:

If it was running fine before i would go through double checking all the basics before replacing the ICM, make sure your engine and chassis is grounded well along with what i listed earlier.


Thats what I spent the last few days doing. Every wire is connected correctly, the car has a 4ga ground from the battery and two 4ga straps from the engine to the body, and every sensor is properly grounded. The ICM harness is also solid.
The fuel pump runs, the car cranks, and the ECM doesnt throw any codes and connects to the OBD2 sensor. All fuses have been properly replaced and have not blown. I have vacuum to the fuel pressure regulator and EVAP. The only thing I have NOT checked is the +12v for the computer, injectors, and other misc sensors.


At this point it almost HAS to be the ICM(and it is grounded). Considering I have +12v to it and its not working. The volts drop to 10 during crank, is that normal?
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Mike Gonzalez
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Report this Post05-27-2015 01:59 PM Click Here to See the Profile for Mike GonzalezClick Here to Email Mike GonzalezSend a Private Message to Mike GonzalezEdit/Delete MessageReply w/QuoteDirect Link to This Post
Never actually had a meter on an ICM while cranking so I cant answer that, but I imagine it would be with the draw of the starter.
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Justinbart
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Report this Post05-27-2015 05:30 PM Click Here to See the Profile for JustinbartSend a Private Message to JustinbartEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you ever swing by the flint area I have a spare you could try.

------------------
Turbo 3800 E85 F23 5spd spec5
10.91@133.1

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Darth Fiero
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Report this Post05-27-2015 05:53 PM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
A working crank sensor and a good ICM will produce a spark while cranking the engine over even without the PCM connected to the harness.

If the ignition key was on and ICM was wired up and connected to the harness when you hooked the battery up backwards, then yes, you could have fried it.

A bad ignition module, bad crank sensor, and/or bad related wiring could all cause a no spark condition. But that's about all that could cause it.

------------------
OVERKILL IS UNDERRATED

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

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Threedog
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Report this Post05-27-2015 09:39 PM Click Here to See the Profile for ThreedogClick Here to Email ThreedogSend a Private Message to ThreedogEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Darth Fiero:

A working crank sensor and a good ICM will produce a spark while cranking the engine over even without the PCM connected to the harness.

If the ignition key was on and ICM was wired up and connected to the harness when you hooked the battery up backwards, then yes, you could have fried it.

A bad ignition module, bad crank sensor, and/or bad related wiring could all cause a no spark condition. But that's about all that could cause it.




Yeah, at this point it is either the crank sensor or the ICM. The wiring is one wire from the E3 of C500 to the ICM harness + good grounds, and since that wire is getting +12v...I hope to god it is not the crank sensor..
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phonedawgz
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Report this Post05-28-2015 03:25 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
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