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Nissan Forum: icm burns up !!!! why????
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  #11  
Old 05-22-2014, 05:41 PM
jp2code jp2code is offline
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Do you have one of these?

d21_truck_1990.pdf

If not, Right-Click it, select Save As, and put that in your My Documents folder.

From there, go to the EC section and find out what kind of voltages the ICM is expecting and what wires go to ground, etc.
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1994 Heavy Duty D21, Long Bed, 2WD, V6, 5-speed
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  #12  
Old 05-22-2014, 09:37 PM
nerdistmonk nerdistmonk is offline
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Well back in like april of 2013, when i was doing that giant ignition conversion i believe i said at that time "The engine computer controls everything via grounds, the whole system uses ground wires to switch sensors on and off", and due to the design of the ICM's they can and almost always wind up permanently switched on because they short somewhere along their ground path to the ECM computer. (and thus blow up)


He needs to identify the ground wire going to the ICM from the computer and then patch a new wire in going directly to it, bypassing the faulty wiring that has found ground somewhere in its path to the computer.

Your entire wiring harness is held together with standard electrical tape from the factory, and that tape does come off over time = short.


I didn't say nothing last night because its not really a procedural fix, your gonna have to eye ball it, all those schematics will tell you is wiring colors also fyi......also the wire colors did change at some point in time because that 1989 .pdf of the fsm is not correct on an 86.5

Last edited by nerdistmonk; 05-22-2014 at 09:42 PM.
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Old 05-22-2014, 09:45 PM
jp2code jp2code is offline
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And he's a Monk - so we know he would not steer us wrong.

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1994 Heavy Duty D21, Long Bed, 2WD, V6, 5-speed
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Trouble Codes for Nissan 1988-1995: http://nissanforum.org/nissan-forum/showthread.php?t=23202
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  #14  
Old 06-06-2014, 02:39 PM
cadillacdude1975 cadillacdude1975 is offline
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im calling a bad distributor or wiring. i told him to change the distrib and see how that goes. he has a parts truck so i believe that will steer him in the right direction.
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  #15  
Old 06-07-2014, 04:14 PM
nerdistmonk nerdistmonk is offline
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Quote:
Originally Posted by cadillacdude1975 View Post
im calling a bad distributor or wiring. i told him to change the distrib and see how that goes. he has a parts truck so i believe that will steer him in the right direction.
What could go bad inside that "distributor"?, all thats in it is an optical pickup.

That optical pickup goes to the computer, not the coils or ICM's, the computer ultimately sends the fire signal to the ICM's.

(the ICM's are off more than they are on, the ground is disconnected via computer, the circuit is closed for a split second by the computer to fire the coil and it does this however fast the engine is turning)

Somewhere in the ICM circuit a ground wire has found a new ground via the body or frame, likely a bare spot somewhere, or even it shorting with another wire.
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