Electrical problem with ‘04 GMC 2500hd

[whitelightnin22]

Hey guys I have an 04 GMC 2500hd with the LB7 duramax engine. The other day I fired her up and I noticed the check engine, ABS, parking brake light and service 4wd on the dash. It was in limp mode driving home. Now it wont fire up or even turn over and keeps blowing ignition fuse A every time I attempt to turn it over. It is throwing codes U2106 and U1024. Loss of communication to TCM and faulty TCM. All the research I have done say the TCM is rarely ever the actual cause and it could boil down to Ignition switch, starter, nsbu switch, etc. I doubt it is the starter since I installed a new one about 3 months ago. I just replaced the ignition switch and nsbu switch within past couple days with no luck. I haven’t seen any exposed/rubbed wires anywhere that I can see. I even pulled plugs from TCM and they looked fine. I really don’t want to haul it to a shop to get bent over a barrel and I dont want to spend $500 on a remanufactured TCM or $1800 on a new one without knowing it truly is the cause. I did notice the battery light on and a low voltage reading when I attempted to install my programmer. Could it possibly be the alternator or???? Any help would be greatly appreciated. Im far from a true mechanic but if its something i can solve myself I would much rather. Thanks guys.

 

[fslc94]

Definitely make sure you have good voltage and batteries are good, check your grounds. I'd test the alternator just to eliminate that as well. Electrical can be tricky

 

[BIKER13]

04 Chevys are notorious for electrical problems. Ended up putting a battery cut off switch on mine.

 

[Stewart]

Make sure that the hot wire to the starter didnt come loose and touching a ground. That could blow the fuse.

 

[THREEJAYS]

Had a buddy with early 2500 that had trouble with mice chewing the wires

 

[smoothhd]

Look under the floor covering where your left foot would rest while driving. There is a wire harness there and the wires chaff. I have fixed several GM trucks of that era that had electrical issues. Harness usually comes through firewall, runs down side of footwell under floor covering.

 

[Scuba dog]

The instrument cluster is known to get water on it and mess up

 

[austin147123]

Purple starter wire on my lmm duramax was rubbed through on side of block kept blowing ignition fuse, worth a look

 

[PA4476]

I would put a charger on the batteries and make sure they are both fully charged and see what happens then.

 

[Lobo1]

I have a 2001 H D 2500 with the same engine, LB7 6.6 Duramax. My check 4WD light will occasionally come on in the Message center box and I just stop, turn the engine off. Start it back up and go on. Then occasionally my ABS light and emergency brake light will come on. Same thing, I will stop, shut it down and restart it. Never blew a fuse and never goes into limp mode so I would be willing to bet yout Main problem is the electrical short. My lights have been doing this for several years. 2001 - 2004 are well known for the instrument cluster to act goofy. sometimes my gauges will flutter, the needles bounce back and forth while the indicator lights flicker. I tap lightly on the plastic cover over the cluster and they stop.