# Current leak through interior lighting kills battery



## PontiacGuy (Apr 22, 2006)

2006 GTO, M6, owned since new, 65K miles.

My car has been very trouble-free but an electrical gremlin has gradually developed. About a year ago I noticed that the battery began dying if the car wasn't driven for a while. Its gradually gotten worse and now the battery is dead after only a couple of days. The charging system seems fine, and checking with a volt meter the battery has a full charge after driving around for a bit. I replaced the battery and that did not help, so I checked the current draw at the battery and it is pulling .140 Amps with everything off and the key out. I opened the interior fuse box and found that if I pull the interior lighting fuse it drops back to .01 Amp. So it looks like I have a current leak through the interior lighting circuit. I checked all the lights including the trunk and everything seems OK.

The only mod I've made is installation of a Pioneer AVIC head unit a few years ago. I used the correct wire kit, soldered all the connections, etc. and it works perfectly so that shouldn't be an issue.

Does the circuit go through the BCM _after_ the fuse? I checked behind the glove box and don't see any signs of abrasion on the wire harness (though I will protect it for the future.)

Any ideas where to look? Is an interior lighting circuit diagram available?


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## PontiacGuy (Apr 22, 2006)

Followup- I left the lighting fuse out overnight and absolutely no drop in battery voltage.

The lighting relay clicks on when I put the fuse in- seems that is what is drawing the power. But no lights come on. Checked everywhere.

Wish this was as simple as my old cars.


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## Ross61 (Jan 27, 2014)

I'd try pulling the radio fuse (cannot recall which one it is but pretty sure it's in the inside box).

If no joy, and as much as a pain as it might be, try disconnecting the negative terminal on the battery for a couple days/nights to determine if the battery is failing.


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## PontiacGuy (Apr 22, 2006)

With the battery disconnected, no problem even after weeks. I've had the lighting fuse out for a couple of days now and I'll check the battery charge over the weekend. I don't expect to see a voltage drop.

One thing I noticed is that there is a lighting relay on the right side of the panel and with the fuse in the relay energizes and stays energized even with everything shut down. That's probably where the drain is. But there are no lights on- checked the trunk, glovebox, etc.

When I first posted this I assumed that the fuse was for interior lights only. Now I'm not so sure. I'll check to see which lights work and which ones don't with the fuse out.


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## svede1212 (Nov 1, 2005)

These cars seem to have significant parasitic battery drain even stock. I gave up and installed a trickle charger in my garage with a cord that drops down from the ceiling. I always plug it in when I park her.


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## PontiacGuy (Apr 22, 2006)

I never had a problem until recently with this one, so something has changed.

I left the interior lighting fuse out and had plenty of cranking power after 1-1/2 weeks, so very sure that the interior lighting relay is what is killing the battery. The relay stays on when the fuse is in even though no lights are lit. So it must be some sort of master and guessing that it gets energized by the BCM?


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## Gotagoat (Jan 6, 2006)

You might want to be sure your glove compartment light is off. I've noticed that my door doesn't always close completely and the light remains on.


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## PontiacGuy (Apr 22, 2006)

The only things that seem to be affected by pulling the fuse are the interior courtesy lights, glove box lamp and trunk lamp. Everything else works fine with the fuse pulled including instrument lighting, headlights, etc.

I've checked to make sure all the lamps are off, and the current draw is only 130mA. Not enough to light a bulb, but enough to drain the battery pretty quickly. Quite sure that is what the relay coil is pulling. I just don't understand why the relay always stays energized.


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## AZDesertDude (Dec 11, 2014)

I know this thread is from 2015, but am very curious if you were ever able to resolve this problem? I have a very low mileage (21,000) 2004 GTO that has this exact same issue. I get a parasitic draw of 160ma on the lighting circuit. It drops to almost nothing when I pull the fuse or the interior lighting relay. Tried replacing the relay as it was inexpensive, but no change. Verified no lights staying on in any compatments by video recording in these locations with my iPhone. Checked the wires going to the BCM, as it is common that they rub through against the metal underdash structure, but all was fine. I am at a total loss. Since we have identical issues, I am hoping you determined the problem.


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## Shaneli (Feb 22, 2017)

Same problem to this old post. My 2005 GTO battery dies after a few day and has been like this for 6 months now without any new mods to the car electronics. Has a parasitic draw of 150 ma and goes down to a normal after pulling the interior illum. (interior lighting) fuse.
New battery, all interior lights have been verified off, trunk light off, glove box light off, ignition key out, new Interior ilum. relay, checked BCM wires for rubbing wear.... Cant seem to figure this one out. Any ideas?


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## GTO JUDGE (May 14, 2005)

Many of these of cars experience a BCM wire chaffing behind the glove box. When removing the glovebox and looking to the upper right there is a sharp angled bracket. The BCM wire from factory lays in the gullet of that bracket which chaffs the wire over time. This has been known to cause electrical gremlins from shorting out electrical items, doors not locking and unlocking correctly etc. From the chaffing a wire will be exposed touching metal. If that cable is damaged or wire exposed and taping it does not cure it you may need a new BCM if the module has been damaged. If the wire is exposed and making contact with metal, maybe it's drawing enough current to kill the reserve power from the battery? Simple fix is to examine the wire and use a cable tie to elevate the wire and tie it off to near the right fender by choosing a satisfactory tie off area. 

If you cannot locate a source of electrical draw take a look see behind the glovebox by dropping it down and removing it and verify that wire has not been chaffed and is making contact with metal.


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