Battery Drain 2008 Chev

downslope · Nov 13, 2015

The battery on my 2008 Chevy 3500 6.0 has been running down if I leave it parked for few days. The battery is about 3 years old, so at first I suspected that. But it seems to take a proper charge (takes 8 hours at 4 amp) and is OK if I use it every day or even every other day.
So today I put an ammeter in the positive cable line with everything turned off and key removed. It showed approx 3 amps and made a little spark when touching the probes. So I am thinking this indicates a problem, but where do I start? Disconnected the 2nd auxillary battery, it still read 3 amp on the starting battery. Tried pulling a few fuses, like Integrated brake controller, backup lights, running lights, some of the trailer light fuses (no trailer connected) but no luck, still shows 3 amp draw.

Any suggestions where to start diagnosing? There are like 70 fuses and circuit breakers, many with cryptic labels for things like AC, ECMs, FI, ABS, etc, etc. I started with the lights because it has those lights with delayed shutoff for when you get out of the truck in the dark it keeps backup lights and cab lights, running lights lit for a while. Could one of the solid state controllers be drawing power somehow? It's a basic work truck, so no power windows, locks, mirrors, defrosters, etc.

Any of you ever have a problem like this? Truck has less than 40K mile.

k0ua · Nov 13, 2015

downslope said:
The battery on my 2008 Chevy 3500 6.0 has been running down if I leave it parked for few days. The battery is about 3 years old, so at first I suspected that. But it seems to take a proper charge (takes 8 hours at 4 amp) and is OK if I use it every day or even every other day.
So today I put an ammeter in the positive cable line with everything turned off and key removed. It showed approx 3 amps and made a little spark when touching the probes. So I am thinking this indicates a problem, but where do I start? Disconnected the 2nd auxillary battery, it still read 3 amp on the starting battery. Tried pulling a few fuses, like Integrated brake controller, backup lights, running lights, some of the trailer light fuses (no trailer connected) but no luck, still shows 3 amp draw.

Any suggestions where to start diagnosing? There are like 70 fuses and circuit breakers, many with cryptic labels for things like AC, ECMs, FI, ABS, etc, etc. I started with the lights because it has those lights with delayed shutoff for when you get out of the truck in the dark it keeps backup lights and cab lights, running lights lit for a while. Could one of the solid state controllers be drawing power somehow? It's a basic work truck, so no power windows, locks, mirrors, defrosters, etc.

Any of you ever have a problem like this? Truck has less than 40K mile.

Pull the connections to the alternator to see if that could be the trouble.. You are going about it the right way, just keep pulling circuits and keep watching the meter.. 3 amps is a bunch.

davesl708 · Nov 13, 2015

I would start with the ground wires. That has been my nightmare chasing down all the ground lugs and getting them tightened back up. There is one under the dash that requires all the dash to be removed to get to it.

As to diagnosing put a amp meter on the positive cable and pull fuses one at a time. You may find the problem moves around. That is what indicated to me it was the ground wire. GM will be no help in locating them either.

Looking4new · Nov 13, 2015

I would disconnect the alternator first, that may be the source of your problem. Then like the others have said, one fuse at a time. Your ECM will still draw juice even with the truck shut off, but 3 amps IS a bunch.

Billrog · Nov 13, 2015

Glove compartment light ?

Wagtail · Nov 14, 2015

What a coincidence, my '07 Toyota HILUX (V6 4.0ltr, petrol) is doing the same thing. I reckoned that it was because I don't drive it for days on end (retired life and all that) and all of the electronics/security systems that are a constant drain over time. 2 year old battery too.

I put a 2W solar battery maintainer on it and that seemed to correct the problem... until I had a bout of overcast conditions. The battery was dead as a doornail, but re-charged fine over night.

Diamondpilot · Nov 14, 2015

I agree with the alternator. Also check the fuel pump. Just had a friend with a 2012 do the same thing because the fuel pump was running in the tank. Thought it might be a simple relay but ended up being the ECM and $1200.

Chris

k0ua · Nov 14, 2015

Diamondpilot said:
I agree with the alternator. Also check the fuel pump. Just had a friend with a 2012 do the same thing because the fuel pump was running in the tank. Thought it might be a simple relay but ended up being the ECM and $1200.

Chris

I wonder what the chances of stuck contacts on the fuel pump relay? The relay is controlled by the ECM, but if the contacts stuck/welded?

Al Mac · Nov 14, 2015

Wagtail said:
What a coincidence, my '07 Toyota HILUX (V6 4.0ltr, petrol) is doing the same thing. I reckoned that it was because I don't drive it for days on end (retired life and all that) and all of the electronics/security systems that are a constant drain over time. 2 year old battery too.

I put a 2W solar battery maintainer on it and that seemed to correct the problem... until I had a bout of overcast conditions. The battery was dead as a doornail, but re-charged fine over night.

I had the same problem with a 2001 Ford Expedition some years ago. I did everything and some other items suggested above. After many hours and weeks I was totally peeved. I ended up taking it to a shop where they tried some things (rechecking my work and extra items) a put a computer in it from the junk yard. Problem solved.

Al
That worked and the rig is still on the road (new owner).