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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1667
Experience:  GM Grand Master Technician 2007. 14 year experience.
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Battery full charged, but have no power. At this point it is

Customer Question

battery full charged, but have no power.
JA: Is the power loss consistent, or does it fluctuate?
Customer: At this point it is consistent. Before this it fluctuated.
JA: What is the model/year of your GMC?
Customer: 2008 gmc sierra
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Have checked wires and relays. Still no power. When I test it, have power going to starter and fuse box.
JA: Anything else you think the mechanic should know?
Customer: Problem starts when trying to start the truck
Submitted: 5 months ago.
Category: GMC
Expert:  Ron replied 5 months ago.

Hello and thank you for your question,

When you say you have no power , is everything dead, do the light come on?

Customer: replied 5 months ago.
Everything is dead.
Expert:  Ron replied 5 months ago.

Okay what model ( 1500 or a 2500) is your Sierra and your engine size?

Customer: replied 5 months ago.
1500
Customer: replied 5 months ago.
Not sure of engine size.
Expert:  Ron replied 5 months ago.

Gas correct ?

How many batteries?

Customer: replied 5 months ago.
Customer: replied 5 months ago.
Acts as if a power cable was broke. When I test it, I get power to starter and fuse box.
Expert:  Ron replied 5 months ago.

There are two mega fuse located in the engine compartment (right rear) . Have a look at the wiring diagram in the link below and start with checking them to see if either one is blown.

https://dl.dropboxusercontent.com/u/104923897/Mega%20fuse%20Jul%2023.pdf

Customer: replied 5 months ago.
I get power out of the mega fuse.
Expert:  Ron replied 5 months ago.

Okay if the mega fuse check ikay then what about all the fuse in the under hood panel, are you getting power on them?

Customer: replied 5 months ago.
I am getting power to the fuse box. I think it is BCM. What can I do to solve this problem?
Expert:  Ron replied 5 months ago.

If you sure its the BCM then it would have to be replaced , have to tried to scan the system and see if there are any fault codes coming?

Customer: replied 5 months ago.
Looks like I will have to take it some where.
Expert:  Ron replied 5 months ago.

I sure would do that before you start replacing parts that may not be needed. If the complete electrical system is dead then I suspect you have a connection issue someplace and its going to be a mater of tracking it down.