[MrCarpenter]

Did you not say 85 on the horn relay to ground is zero ohms? If 86 has 12 volts, and 85 is connected to ground, then your relay will change states.

Right. Thats right.

 

[MrCarpenter]

Thank you for bearing with me, I really appreciate all your help.🙂

Another question, along with an update.

I unplugged my bcm completely, and the horn now works perfectly fine. The truck obviously doesn't run without the BCM. So, I plugged all the connectors into the bcm except the one that makes the horn beep. Now everything but the horn and lights works on the truck. As soon as I plug that last connector into the bcm, lights and horn go on. So... obviously the horn and lights are grounding out through the BCM connection. Does this indicate a failed BCM? Or is it still a short somewhere that throwing the BCM off?

 

[peewee0413]

It's the BCM thats causing it for sure. The BCM has your alarm system. 85 from your relay splits. One wire to the horn switch the other to the BCM. Now is the BCM bad, or are you in some weird state i know nothing about?

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[MrCarpenter]

It's the BCM thats causing it for sure. The BCM has your alarm system. 85 from your relay splits. One wire to the horn switch the other to the BCM. Now is the BCM bad, or are you in some weird state i know nothing about?

That's what I'm really wanting to find out. If I unplug all the connectors from the BCM except that one, it honks and lights come one. So the issue is isolated to that connector.

 

[MrCarpenter]

Would it be damaging to another vehicle to plug my BCM into it to see if the problem is replicated?

 

[MrCarpenter]

So do I need to check all the wires on that connector for a short? How do I do that? If one wire is shorting to ground, how can I tell that with a multimeter?

 

[MrCarpenter]

I don't really know how to use a multimeter...

 

[peewee0413]

Would it be damaging to another vehicle to plug my BCM into it to see if the problem is replicated?

Not sure, someone here may let you know if the BCM can be swapped. I don't know what security problem will arise.

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[MrCarpenter]

Will the BCM be able to ground a circuit on its own? The circuits are switched to ground, right? So something has to be grounded out for the bcm to be able to ground... right?

So one of those wires on that one connector must be grounded?

I'm thinking too hard, my head is starting to hurt...

 

[peewee0413]

Yeah, the bcm has a way to switch the horn and light circuit on and off to set off an alarm.

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[MrCarpenter]

So I may need a new BCM...

 

[peewee0413]

Maybe

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[shakenfake]

Swapping BCMs would do nothing because the security mode will activate in the other truck.

 

[peewee0413]

Swapping BCMs would do nothing because the security mode will activate in the other truck.

Would need programming right?

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[shakenfake]

Correct

 

[MrCarpenter]

I swapped the bcm, and now the truck runs and drives great, and the horn and light issues are resolved.

Yes, it needs programming, but I have a nice little loophole. My aftermarket remote starter will start the truck, and then I can key on and drive it. Seems to bypass the security.

Truck is going to get programmed on Thursday.

Thanks for the help guys. Especially @peewee0413

 

[GBSierraSLE]

Awesome! Thanks for posting the update.