2018 Savana (just pretend it's an Express) without factory tow package.

I have an 04 Express and an 05 Express - without factory tow package. So I added a 10,000 lb, receiver to each, added a plug & play trailer light harness and towed whatever I want.

But on the 2018 I did the same things and then had no right rear turn signal or brake light. A new bulb and fuse didn't fix it but giving the dealer $1000. for a new bcm did. Before the dealer lads Started working the service manager assured me that they would get all the lights, including the trailer lights, working. After I paid them and soon after that I discovered that all they had done in regard to the trailer lighting was to unplug the plug & play trailer lights harness and leave it hanging there. When asked they denied that they said they would also have the trailer lights working. The guy who assured me - the service manager - said: Sir; no one here told you that!

The mechanical said: You probably overloaded the bcm relay contact.

--------------------
Are the right and the left bcm relay contacts the same strength?

Yes.

Well; the left side works fine, even with the trailer connected, so how did the right side of the truck overload if the exact same loading has the left side still happily playing nice with others?
-------------------

My question now is: is the bcm different based on whether or not the truck has the factory towing package?

Is it therefore impossible to tow with a no-factory-tow-package truck?

At $1000. a pop it is a damned expensive trial & error issue.

 

So far as I can see, there’s only one bcm part number for your van, 84922494, and it’s used on a bunch of different GM cars and trucks. Seems unlikely running a trailer harness should cause an issue with it.
Is it possible the issue is with the aftermarket trailer wiring system you bought?
BTW, Amazon sells that genuine GM bcm for like $115. Stealership strikes again.

 

Thanks. That would have been my logic based conclusion.

Although I guess the bcm programming could be different between the two (factory towing vs no factory tow package) for some reason. <g>

I only agree to spent the $1000. at the dealership . . . . because they assured me that they would make sure that all the lights - including the trailer lighting - would be working when they were done with the truck. And I thought that Them handling it all - with single-source-responsibility - seemed like the best and most straight forward way to go. Of course in the end that was all just smarmy lying dealership-talk.

Speaking of Amazon; that is where I bought the plug & play kit. I have no idea if it's AFU or not - that's what Paid the lying bastards at the dealership to find out.

I didn't pay much attention at the time but now thinking about it; it probably was a Chinese knockoff.

This time I bought a Curt kit from etrailer instead. I intended to install it today but the day wasn't long enough so it got bumped to tomorrow.