04 LB7 IGN 0 Fuse keeps blowing! - Chevy and GMC Duramax Diesel Forum
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Old 09-09-2010, 10:31 PM   eBay Motors  #1 (permalink)
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04 LB7 IGN 0 Fuse keeps blowing!

Ladies and Gents!

I thought I had this problem solved as the truck has been running great for the past two weeks!
I replaced the NSBU switch, along with the ign 0 fuse found on the drivers side dash fuse box. I also removed the two ground wires found underneath the drivers door, sanded the undercoating off, put the wires back on and painted.
The truck has run with no problems for about 700 miles.

Tonight I replaced the Ignition switch.

Yesterday the same problems developed that happened two weeks ago.
Limp mode - 3rd Gear only, harsh clunk in reverse and drive.
No indicator for PNRD3
Speedometer and trans temp at zero
ABS and service brake on DIC
and IGN 0 fuse blows.
No codes are displayed
Tach, oil pressure, water temp, voltage all work.

The IGN 0 fuse blows even with the connectors disconnected from the NSBU as soon as I turn the key to the "on" position.

My theory is that there is a short in the wiring harness with the pink wires going from the IGN 0 fuse to the transmission NSBU switch.

However I also notice in the schematics, the pink wires also connect to the VCM and the PCM.

Any help is appreacited.

Thanks

Last edited by Basshole1; 09-09-2010 at 10:43 PM.
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Old 05-27-2011, 10:32 PM   eBay Motors  #2 (permalink)
 
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I'm having the same problem as you. Did you ever get that taken care of? I did replace the NSBU switch and that didn't fix the problem.
The truck stopped clunking into reverse or drive. The shift indicator is gone, the speedo and trans temp works, the service brake system went away,
the truck seems locked into 3rd gear, but I can go up to 70mph like normal. I replace the IGN 0 fuse, turn the key and it blows with a spark.

I inspected for any cut wires and couldn't find any. Should I buy a new IGN Switch?

I would like to get this figured out without taking it to any stealerships.

Will driving the truck with the IGN 0 fuse out hurt the truck?

Any help would be great!

Last edited by dmax1983; 05-27-2011 at 10:36 PM.
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Old 05-28-2011, 01:22 AM   eBay Motors  #3 (permalink)
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I have had a similar problem in the past, just my IGN 0 fuse was not blowing, IGN 0 fuse is TCM (IIRC)...check DDM fuse or drivers master switch, mine was gummed up/dirty best I could tell. So I took door panel off, took switch apart, cleaned, all was good.

I assume you have power windows? So...

You could pull the DDM fuse and see if it all works correctly.. You might have to turn key on/off a couple of times, to cycle whatever setting, I have had to wait a couple minutes in between. You could try leaving the DDM fuse out but you will not have use of drivers power window functions. You can replace once vehicle is on to restore use of master window switch, if fuses blow or symtoms happen you know source, if not... whats 2 seconds to pull a fuse.

If you find DDM is bad, and are to buy a new DDM it has to be programmed by dealership, so I would suggest to try cleaning connections or pulling fuse to get it to work.

I hope this makes sense it worked for me took me couple days of testing all connections with multimeter and researching before I found only other guy that suggested DDM was culprit.

DDM is connected to transmission it auto-locks the doors when you begin driving, if it is shorted it could cause transmission troubles.

DDM is drivers door module ... basically drivers master power window switch. who would have thought....

I have a 2005 LLY... and yours maybe different, thought I might give it a shot and point you in a direction, or maybe I typed all this for nothing...LOL
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Old 05-28-2011, 08:41 AM   eBay Motors  #4 (permalink)
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Quote:
Originally Posted by dmax1983 View Post
I'm having the same problem as you. Did you ever get that taken care of? I did replace the NSBU switch and that didn't fix the problem.
The truck stopped clunking into reverse or drive. The shift indicator is gone, the speedo and trans temp works, the service brake system went away,
the truck seems locked into 3rd gear, but I can go up to 70mph like normal. I replace the IGN 0 fuse, turn the key and it blows with a spark.

I inspected for any cut wires and couldn't find any. Should I buy a new IGN Switch?

I would like to get this figured out without taking it to any stealerships.

Will driving the truck with the IGN 0 fuse out hurt the truck?

Any help would be great!
dmax1983 - Yes, problem was solved. There is a wiring harness inside the transmission pan. One of the wires had rubbed the insulation off and was shorting inside the pan. Replaced the harness and problem went away.
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Old 05-28-2011, 07:01 PM   eBay Motors  #5 (permalink)
 
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Quote:
Originally Posted by AdamAnt View Post
I have had a similar problem in the past, just my IGN 0 fuse was not blowing, IGN 0 fuse is TCM (IIRC)...check DDM fuse or drivers master switch, mine was gummed up/dirty best I could tell. So I took door panel off, took switch apart, cleaned, all was good.

I assume you have power windows? So...

You could pull the DDM fuse and see if it all works correctly.. You might have to turn key on/off a couple of times, to cycle whatever setting, I have had to wait a couple minutes in between. You could try leaving the DDM fuse out but you will not have use of drivers power window functions. You can replace once vehicle is on to restore use of master window switch, if fuses blow or symtoms happen you know source, if not... whats 2 seconds to pull a fuse.

If you find DDM is bad, and are to buy a new DDM it has to be programmed by dealership, so I would suggest to try cleaning connections or pulling fuse to get it to work.

I hope this makes sense it worked for me took me couple days of testing all connections with multimeter and researching before I found only other guy that suggested DDM was culprit.

DDM is connected to transmission it auto-locks the doors when you begin driving, if it is shorted it could cause transmission troubles.

DDM is drivers door module ... basically drivers master power window switch. who would have thought....

I have a 2005 LLY... and yours maybe different, thought I might give it a shot and point you in a direction, or maybe I typed all this for nothing...LOL
I pulled the door panel, pulled all the DDM connectors and they were all clean, dry with straight pins. Then I put another IGN 0 fuse in with the DDM deleted, turned the key on and the fuse blew.

After that I pulled the DDM fuse with DDM and door panel back in place, turned the key on and the windows didn't work. Put another IGN 0 fuse in, turned the key, didn't blow. But I cranked it and the fuse blew.

Put the DDM fuse back in now the windows work. I think my DDM is good.
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Old 05-28-2011, 07:08 PM   eBay Motors  #6 (permalink)
 
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Quote:
Originally Posted by REFloyd View Post
dmax1983 - Yes, problem was solved. There is a wiring harness inside the transmission pan. One of the wires had rubbed the insulation off and was shorting inside the pan. Replaced the harness and problem went away.
I pulled my trans pan, inspected the wiring harness and didn't see any wires rubbing. Nothing look out of the ordinary.
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2004 LLY 2500HD GMC Sierra 6.6 Duramax
S&B CAI, MBRP Down-pipe, BD Exhaust Manifold,
MBRP 4 inch Exhaust, Sinister EGR Delete Kit,
PPE Standard, AFE Turbo Mouth Piece,
AFE Intercooler Tube Combo, Cobalt Boost Pyro
http://www.youtube.com/user/DieselPowerTV
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Old 05-28-2011, 07:18 PM   eBay Motors  #7 (permalink)
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Quote:
Originally Posted by dmax1983 View Post
I pulled my trans pan, inspected the wiring harness and didn't see any wires rubbing. Nothing look out of the ordinary.
You cannot tell by looking at wires if they are bad or good. Youu need an amp meter and check load. Ohms don't tell you much and neither does voltage. You can have 12V and it will pass voltage on a single strand of wire but will not trigger a solenoid because of low amps.
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