# Duramax electrical problems, please help



## dk2429 (Mar 27, 2015)

Truck is a 2006 Silverado 2500HD, LBZ Duramax/Allison 6 speed. Just rolled 201k miles today. Cold air intake, 100hp PPEI Kory Willis tune, EGR delete. 

I've been having this problem off and on for about 2-3 weeks. ONLY in the morning when i go to start up, truck starts right up fine no issue, and runs perfect. However, here are my issues..

-The lights on the dash are dimmer than normal
-My RPM gauge goes completely crazy when I put on cruise control (cruise light doesn't come on but cruise does work)
-A/C doesn't work
-Blinkers don't work

Here's the weird thing.. After about driving 5 miles, it throws a MIL, and everything works perfect. Blinkers are back, cruise/rpm normal, AC back, light are bright as they should be. The codes im getting in the MIL are P0646, P0381, and P0650. All are related to low voltage. So I pull over and use my scan tool to clear the codes, and then no more check engine light the rest of the day, everything is normal. However, today i had to clear the codes 2-3 times because the problems came back shortly after. Here i am now, no MIL and everything is fine. BUT, it will happen again in the morning. This started happening about 2 weeks ago. It didn't come back all last week, but all of a sudden a few days ago , here we are again..

I had the batteries and alternator tested. Both tested as good. No blown fuses, nothing abnormal I can see. 

I also should note.. I had gotten an Edge CTS2 Insight, and the problems started the next morning after installing. I ended ripping that thing back off, unhooked the batteries to reset ECM, and all was good. But a week later, we're back at it again.

Sorry for all the reading, im just giving as much info as I can. I'm stumped! Anyone can help with this?


----------



## rglide09 (Mar 21, 2012)

Are the batteries showing 14 volts when started cold? My 2002 Dmax runs for about 30-45 seconds before the alternator kicks in. This happens only on a cold start. 


Sent from my iPhone using Tapatalk Pro


----------



## floppodog (Dec 19, 2012)

I think you have a ground problem somewhere. If could be in one of the Amphenol connectors or corrosion. Been washing the engine lately? Look hard..


----------



## rglide09 (Mar 21, 2012)

Definitely check the grounds, one of my batteries has a loose ground and sounded like the starter was going out. May take the ground cable off the engine and clean it and the location on the engine with a wire brush.


Sent from my iPhone using Tapatalk Pro


----------



## dk2429 (Mar 27, 2015)

rglide09 said:


> Are the batteries showing 14 volts when started cold? My 2002 Dmax runs for about 30-45 seconds before the alternator kicks in. This happens only on a cold start.
> 
> Sent from my iPhone using Tapatalk Pro


Got home and cleaned battery cables. They were already clean but did it anyway. Decided to get a DVOM and test batteries/alternator myself (O'Reilly's tested the first time.) Alternator is putting out 14v, batteries are 14v with truck running.. however, with the truck off both read exactly 12.78v. Think i found my issue!

Went to the shop that does my work for me and told him the issue. He said put the batteries on charge overnight. If it doesn't do it in the morning, Batteries are the suspect. If it does, he told me to bring it in and he'll diagnose free of charge.

Maybe O'Reilly's needs a new battery tester???????


----------



## bigdav160 (Aug 25, 2004)

!00% charged battery should read ~12.6 volts. That doesn't seem to be the problem.

I agree there's a connection problem. It could be a ground but also could be on the power side. If it was at the battery it would be affecting the headlamp/tail lamps also. I bet it is a loose ground on the engine somewhere. I don't have my books with me to tell you where to look.


----------



## dk2429 (Mar 27, 2015)

bigdav160 said:


> !00% charged battery should read ~12.6 volts. That doesn't seem to be the problem.
> 
> I agree there's a connection problem. It could be a ground but also could be on the power side. If it was at the battery it would be affecting the headlamp/tail lamps also. I bet it is a loose ground on the engine somewhere. I don't have my books with me to tell you where to look.


Put batteries on charge over night. Started up, everything was good! But as soon as i turned cruise control on, everything stopped working again. MIL came on, cleared the codes, and no problem the rest of the day


----------



## dk2429 (Mar 27, 2015)

Taking it to a shop today I've had my work done at. He offered to diagnose it free of charge. Im ready to get to the bottom of this BS.


----------



## Charlie in TX (May 4, 2012)

If I recall, you didn't start having problems until you installed some type of programmer. My bet is something is messed up in the computer and needs to be reflashed.


----------



## dk2429 (Mar 27, 2015)

Charlie in TX said:


> If I recall, you didn't start having problems until you installed some type of programmer. My bet is something is messed up in the computer and needs to be reflashed.


Yes sir you are correct. It wasn't exactly a programmer though, it was just a monitor. He told me it COULD be the problem, but most likely its not. If it needs reflashing he'll do it for me.

If that is the problem, I have an Edge Insight CTS2 for sale if anyone wants it.. lol


----------



## Blank Czech (Jul 26, 2016)

Did you find out what it was?


----------



## dk2429 (Mar 27, 2015)

Blank Czech said:


> Did you find out what it was?


Took it to the shop I have a good connection with to have them check it out. Apparently #1- there was a loose connection to the batteries (I don't know where, but I made sure battery cables were tight.) And #2 the glow plug control module was staying on when I cranked it up. I put the Edge CTS2 back on the truck and no problems.. I suppose it was just a coincidence. All is good now. Very weird occurrence. Best part is he didn't charge me for anything.


----------



## reba3825 (Feb 28, 2013)

I hope you tipped him.


----------

