'05 Chev Half-Ton Electrical Issue

[LBZ]

My brother has an '05 Gasser Chev 1/2 ton and is having a weird issue with it. First off, the switches for the power seat decided to go retarded and are now functioning backwards for some reason. He didn't touch anything.

Second, his trailer plug is also acting up. When he turns his left signal light on, the right one blinks as well-only in the plug, the truck lights are fine. He unplugged the GM trailer socket from the wiring harness and tested it with a test light and was still getting power to both the left and right signal wires at the same time when the signal light is on. Again, the truck lights are fine, only the trailer lights are affected. This is also an intermittent problem that happens about 50% of the time.

Could these be a BCM issue or something? The wiring in his truck is identical to ours from what we can tell. The harness goes back up to the front and disappears so it's gotta be coming from up there somewhere. There does not appear to be any pinched wires or anything that he could find.

Any ideas????

 

[DAVe3283]

I had the same turn signal problem on my '03 Duramax. There is an electronically controlled relay board monstrosity they call the flasher module located on the back side (IIRC) of the driver's door fuse panel. PITA to get to. Mine had a bad relay, and it did exactly what you were describing (both trailer lights blinked, but the truck worked fine).

Rather than buy a new one, I took mine apart and saw a relay with a bent contact arm (WTF???). I used a screwdriver and un-bent it (seriously, how the heck did it get bent in the first place???), and it has worked ever since.

You might have to buy a new one, though. I considered making a solid-state one so there were not relays to wear out, but when I fixed mine I lost the incentive. Plus, they would cost like $75, although they'd last forever...

 

[03Tommy]

My 03 Duramax did the seat thing. A guy I knows 05 suburban did it as well. Never really looked into how to fix it.

My 05 denali has a weird signal issue. It is kinda like what you described but it is on the truck and not trailer. Left signal works fine. Right blinks both but not all the time. If a trailer is hooked up the trailer is fine. This just happend a few days ago so I havent dug into it.

 

[68skylark455]

We have had several of these trucks do strange things with the lights. Most common is a blow rear pass light fuse in the under hood fuse box. The next thing is the mulitfunction switch in the column ie turnsignal switch. The wires on the back of it are very small and break very easy.

 

[krock05]

I had the same turn signal problem on my '03 Duramax. There is an electronically controlled relay board monstrosity they call the flasher module located on the back side (IIRC) of the driver's door fuse panel. PITA to get to. Mine had a bad relay, and it did exactly what you were describing (both trailer lights blinked, but the truck worked fine).

Rather than buy a new one, I took mine apart and saw a relay with a bent contact arm (WTF???). I used a screwdriver and un-bent it (seriously, how the heck did it get bent in the first place???), and it has worked ever since.

You might have to buy a new one, though. I considered making a solid-state one so there were not relays to wear out, but when I fixed mine I lost the incentive. Plus, they would cost like $75, although they'd last forever...

Ok thanks! so how exactly did you get to the flasher module? Any help greatly appreciated!

 

[DAVe3283]

Ok thanks! so how exactly did you get to the flasher module? Any help greatly appreciated!

You have to take the "knee bolster" off, then reach up under the dash.

When removing the knee bolster, GM says you have to remove the trim bezel, but I don't think I had to, so you can probably skip that step.

Hope this helps!
~David

 

[Madspeed]

My brother has an '05 Gasser Chev 1/2 ton and is having a weird issue with it. First off, the switches for the power seat decided to go retarded and are now functioning backwards for some reason. He didn't touch anything.

Second, his trailer plug is also acting up. When he turns his left signal light on, the right one blinks as well-only in the plug, the truck lights are fine. He unplugged the GM trailer socket from the wiring harness and tested it with a test light and was still getting power to both the left and right signal wires at the same time when the signal light is on. Again, the truck lights are fine, only the trailer lights are affected. This is also an intermittent problem that happens about 50% of the time.

Could these be a BCM issue or something? The wiring in his truck is identical to ours from what we can tell. The harness goes back up to the front and disappears so it's gotta be coming from up there somewhere. There does not appear to be any pinched wires or anything that he could find.

Any ideas????

I know for a fact its not a bcm issue the trailer wiring is all to do with the turn signal switch they use 2 switches in one and 2 seperate circuits to run trailer and turn signals.IIt is actual a very nice system and I tried my ass off to use it in my Blazer. its your turn signal switch Ive had them apart and I know this wiring like i know many parts of my own body. FFS I married it to my 1972 blazer. I probebly know more than GM about the electrical in these trucks
The seat thing needs rthe module reflashed. I Dont know why they do it but they do. My wifes did the same shit i could see the pid requesting seat up and the friggin thing went down and vise versa. We reflashed the module and it fixed it

 

[LBZ]

Thanks Madspeed. I think he's registered here now and may have read this.

He's looking into the issue!

 

[LBZ]

Well he pulled the flasher thingy out and opened up. Went yup that's alot of crap I don't understand, put it back in and now everything works fine.:rofl:

I'm guessing it's got a broken wire or solder on the board somewhere. This probably won't be the last time it happens to him but at least he knows where to look next time

Thanks guys!