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Driver side fog light and taillight will not turn off

Tiny
TOMMYROBERTS
  • MEMBER
  • 2009 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
Driver side fog and taillight stays on when truck is on and off. Truck wasn’t starting so I replaced the ECU and the ignition switch now just have the light issue so far. Swapped the relays around with no luck, my other relays could be bad too though. All the issues started in one night and I believe it may have been close to a lightning strike. Thank you for any help.
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Sunday, July 10th, 2022 AT 4:07 PM

11 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

I need you to try something for me. First, understand this isn't making sense because both the left and right fog lights have the same power supply. See pic 1.

What I want you to try is this. Remove fuse 26 in the under-hood fuse box. That should turn both fog lights off.

I'm asking this because if it doesn't, we are getting power to the left side from somewhere else. The ground is located on the left lower section of the radiator support, so power could be coming in from there. The right fog light ground is on the opposite side.

At this point, I can't see how a relay, fuse or anything would only power one side constantly. As far as the taillight, is it the parking light, brake light, signal, or all of them staying on?

Let me know.

Take care,

Joe

See pics below. Pic 2 shows the fuse to check. Note: Remove fuses 26 and 28. The wiring schematic and the fuse box legend show different things.
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Sunday, July 10th, 2022 AT 10:27 PM
Tiny
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Hey Joe,

I pulled fuses 26 and 28 and the lights stayed on and noticed that the radio and A/C controls stayed on as well. I just realized that the blinkers are not working, high beams are not, and I can’t control the lights with the internal switch. The inside overhead lights are not controllable either.

Thank you, Tommy
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Monday, July 11th, 2022 AT 5:38 PM
Tiny
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  • MECHANIC
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Hi,

We have a short to power from a different circuit. Do me a favor. Remove one fuse at a time to see which one turns the light off. We need to narrow this down.

Joe
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Monday, July 11th, 2022 AT 8:07 PM
Tiny
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Joe,

I found that the j-case fuse #72, “left bussed electrical center 2” turned off the lights inside and out.
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Tuesday, July 12th, 2022 AT 6:13 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,700 POSTS
Hi,

That fuse powers the left interior fuse box. The one you indicated is in the under-hood fuse box where the fog lights get power. If I had to guess, something has melted under the fuse box and is sending power all the time or the BCM has failed.

Here is what I suggest. Disconnect the battery. Remove the fuse box where the fuse is located and inspect the wiring, connectors and the fuse box itself for evidence of overheating or damage.

I attached the schematic showing the power distribution for that fuse.

Let me know,

Joe

See pics below.
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Tuesday, July 12th, 2022 AT 8:24 PM
Tiny
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Joe,

I pulled the fuse box, and the connections looked good, going to go with the new BCM also I cranked it and it stalled out in idle one time. So, I believe it’s another sign of the BCM as well. Thank you and I’ll let you know how it works.

Tommy
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Wednesday, July 13th, 2022 AT 6:46 PM
Tiny
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  • MECHANIC
  • 109,700 POSTS
Hi,

Thank you for the update. The idea that it stalled shouldn't be related to the BCM, but anything is possible.

Let me know how things turn out for you. Also, I attached the directions for replacing the BCM below. Note, if you are replacing the BCM, it will need programmed. I attached the directions for that as well after the replacement directions.

You may want to check online to see if you can get a remanufactured one that is plug-and-play, but that's up to you.

Let me know how things turn out or if I can help in any way.

Take care,

Joe

See pics below.
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Wednesday, July 13th, 2022 AT 9:57 PM
Tiny
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Hey Joe,

I replaced the BCM, and it solved almost all problems, the interior dome lights stay on continuously though, all other light switches work fine now, head light controls, blinker, fog lights, etc, work great now. I’m thinking about replacing the light/dimmer switch now?

Thank you, Tommy
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Saturday, July 23rd, 2022 AT 7:36 PM
Tiny
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Tommy, I'm glad to hear you got this far. As far as the interior lamps are concerned, the BCM should have taken care of that as well. I wonder if there is a door switch that failed. When the door is closed, the switch is open. So, what you would need to try is disconnecting one door switch at a time to see if one turns the light off.

It's a thought.

Joe
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Saturday, July 23rd, 2022 AT 9:35 PM
Tiny
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Got it, I pulled the #5 inside, dome light fuse and put it back in and everything works great. Don’t understand why, maybe a reset. Lightning does strange stuff to vehicles I guess. Thank you very much! It was a mess and I couldn’t fixed it without your help

Thanks again, Tommy
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Monday, July 25th, 2022 AT 7:43 PM
Tiny
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  • MECHANIC
  • 109,700 POSTS
Tommy:

You are very welcome. I'm glad to hear you got it working. Also, thank you for the update. It must have reset something with the BCM. Ugh! Nothing is ever simple. LOL

You take good care of yourself and please feel free to come back anytime in the future. You are always welcome here.

Joe
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Monday, July 25th, 2022 AT 8:32 PM

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