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My park lights are staying on all the time when the truck is shut off. Sometimes they will be off after starting the truck and shutting it off, but then closing the hood or the door seems to bump something and the park lights come on. Pulling any park light fuses and relay does nothing. They don't shut off after 15 minutes with the power saving stuff either. Any ideas?
 

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Hmm I had hoped Max Power would see this and post...
 

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Lots of components to the system. Is it under warranty?

What is all in the truck for aftermarket electrical?
 

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Just the stuff in his sig, stereo system. Been there for months, only connected by the adapter to the radio harness and the big amp wire to the one battery. I had put the wires on it for the MP all lights on mod a few weeks ago, but we pulled them back off today.

I pulled every fuse in the underhood box, no change. So it almost has to be that some wire underneath there is touching another. Otherwise we should be able to kill part of the circuit with the fuses. It would shut off sometimes after running the truck and shutting it off, but then you close the hood or door and it would come back on, which also lends to my theory of a loose wire crossing somewhere under the fuseblock. He's gonna take it in monday afternoon and they'll pull the fuseblock out and check it since it's under warranty. He pulled the negatives on the batteries for the night.
 

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Pulling the park light fuse should kill the park lights. Pretty much has to.

I would disconnect the park light switch and see if it still sticks on. That will either narrow it down or eliminate the park light switch.

Try swapping relays with headlamps or something. See if the headlamps start doing it instead of the park lights. That will verify or eliminate the relay.

Then you are down to BCM or wiring.

No remote start?
 

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No remote start or anything else.
I pulled all the fuses and relays, first the ones for the park lights, then any related to lights, and then all the rest. With none of them in it still lit the park lights. So we were down to wiring or the switch. Didn't feel like pulling the switch because it was cold in the shop so we gave up for the night. Might try that tomorrow. But if I had the fuses pulled and it was the switch then it should have shut off right? That was why I figured it has to be a wire crossed underneath. Or something crossed up in the bcm maybe? It's more than one circuit looks like by the wiring diagram I think...
 

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If you pulled the park light relay they almost could't come on. Does he have a brake control?
 

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If you are sure you pulled the park light fuse and the park lights are on that means that the park lights are shorting to +12v after the relay.

There are really only 2 places where this is likely to happen.

The trailer plug in the rear. Check for something metallic in the plug shorting it out to power. Try disconnecting the wiring from the plug. Check the wiring to make sure it is not beat up from stones where it drops down to plug into the plug.

The 2nd place is at the brake control harness. Try disconnecting the plug from the junction block.

If the lights come one when the relay is pulled I will bet money on one of these 2 places causing the problem. Rear plug is my guess.
 

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No brake controller either, but I'll check those tomorrow. Thanks.
 

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You can also follow the trailer wiring back to the junction box at the rear and disconnect it right there. That will eliminate the trailer plug completely.

Does he travel a lot of gravel?

There are lots of places this could happen but the most likely is definately the rear plug.

Also try pulling the trailer B+ fuse.
 

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You know I thought about the trailer plug, made sure to pull the fuse for that but then didn't think of checking the plug and harness at the back...

Yeah it's always on dirt roads, around the farm and stuff.

Trailer b+ fuse is the one in the fuseblock there, or another one to energize the trailer brake?
 

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It's the one on the very front passenger side corner of the underhood fuse block.
 

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Hmm, that one just looked like a plastic cover thing... Our trailers don't have brakes, the ones he pulls anyway. The hitch had never even been used when he bought the truck, so no one must have put a fuse in there. It said b+ on it so I thought it was something like that.
 

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Then he has a shunt and perhaps I am barking up the wrong tree.
 

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Oh well.. We'll let the GM tech mess with it monday and see what he finds. Thanks though.

We just posted this earlier because we had hoped it would be easy and not have to take it in, but after pulling all the relays and fues we realized it wouldn't be.
 

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I think the GM techs will have a hard time with this. Too bad you weren't closer, I like finding problems like this :D I bet I could find it in under 1/2 hour if it was in front me. It's just a matter of isolating circuits until you can narrow the source down. The hardest part is it pretty much has to act up to be able to find the problem.
 

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I hope they don't have too hard a time... The guy that will do it is the best guy they have there... It's too bad he isn't the duramax/allison tech, then I would trust them to work on my truck. He is pretty good with GM trucks in general though, when dad and I had 2000 1/2 tons he was a lot of help.

If they don't figure it out though, we might have to visit you anyway... ;)
 

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If you have the Camper Wiring Harness option, (located on top of frame between cab and box), check that out for gunk or shorts too.
Someone else recently had lighting issues and this was their culpret.
http://dieselplace.com/forum/showthread.php?t=52859&highlight=camper+plug

If you removed the PARK LPS Fuse 30A, (Fuse Block-Underhood), this should have eliminated a stuck Park Lamp Relay, (Relay Block-Body).
I'm not familuar with the b+ fuse, (must be a 2004 thing). The +12V, (hot at all times), on my 2002 is from STUD 1 MaixFuse 40A, red wire pin E on Trailer Connector. That pin E should be the only terminal +12V at all times on the Trailer Connector.
Info from Helms 2002.
 
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