2007 - 2500HD (NBS) 6.0 Z71 Electrical Gremlin (BCM Issue?)

lvgmman · October 4, 2016

so first post, this is actually my dad's truck and we are both starting to run out of ideas.

This started as an intermittent no crank truck is a 2007 6.0 2500 z71 new body not classic with ~100k on it. The battery has been replaced with no change. The remote keyless would not work. when you opened it manually there would be no dome light, no ability to roll down the windows no dash lights nothing with the key to run, would not crank. he would get out check the ground on the battery no change. He stated that he would leave the battery disconnected for about 10 minutes then reconnect it and fiddle with the key in the door lock not the ignition and the dome lights would come back on eventually and everything would act normal and he could start the truck.

He did some investigation and decided it was the battery ground and replaced it with the oem cable. keep in mind we are in NV there are no signs corrosion of any type on this truck. The replacement ground did nothing to change this intermittent condition. He then took it to a local dealer who stated they performed the BCM update (i wish i could tell if it was for sure done). No change. randomly this truck will act 100% dead and after fiddling with the power and driver door lock it will work again hot or cold engine did not matter it was random..

At this point he asked my opinion and after a fair amount of research I had him order a replacement starter as all signs pointed to an electrical issue or break at the starter after we tested the ignition switch and all relays up to the starter. he ordered a re-man ACDelco starter and installed it. The issue with a completely dead truck has now gone away but has presented a new issue. He regularly has to sit in his truck to write invoices. Now that the summer has finally ended he doesn't have to sit there idling anymore with the a/c on. This is how we located the repeatable issue. When sitting there for 10-15 minutes with the radio on the radio eventually cuts off normally as it should. Once that happens and he tries to turn it back on or start the truck it won't start the only thing that happens is the Service 4wd is displayed in the cluster. at that point he says he gets out pulls the battery connections for about 30 seconds and then reconnects and the truck fires up again.

my frustration with him is he has one of the super fancy snap on code readers almost always sitting in his lap at the same time this is going on but he hasn't connected it to see what the computer is telling him is going on. instead of doing that he is essentially clearing the only thing that will tell him what is going on. Based on the description of this issue I am starting to think he has a BCM issue where it is loosing comm with the 4wd causing a no start but it is just a shot in the dark until he can provide me with some scanner data. He was quick to tell me that the starter didn't fix the issue but as i see it this is a completely different issue now.

pending the code data but has anyone had a similar experience? from what I have read the service 4wd display is basically a catch all and if the issue is the same on a 2wd it would just say service stabiltrac or something to that effect. The BCM clearly controls the battery run down features that is why i am leaning towards the either the BCM failing or the reprogram not being completed properly.

davester · October 4, 2016

why blame the reprogram, since the truck works the same before and after it happened...

maybe check that the bcm is getting good reliable power and ground signals and that the connectors are all properly seated and don't show any signs of corrosion.

lvgmman · October 5, 2016

The question is really how is the bcm update performed? Dealer says the bcm is bad and now needs to be replaced. I'm not blaming the update I'm blaming my dad for having the update done rather than replacing the starter first like we troubleshot. Now the bcm update was done and we have this new issue and the dealer says the BCM is now bad and needs to be replaced.