I thought my 2009 H3T Alpha BCM nightmare (https://www.hummerforums.com/forum/h...ghtmare-48657/) was over after a seemingly successful BCM clone, but I was wrong. The key fob worked again and I was able to sync all four tire pressure sensors. I even cleared the P0315 crankshaft position sensor relearn. Everything else seemed to be working too until today when I discovered that the rear window defogger won't turn on now.

But when I select it with my Vident Ilink-400 scanner, I can toggle it on and off (the orange indicator light in the button illuminates). It just won't activate by pressing the button on the console. There are no B-anything codes set. It was working fine with the original BCM (the one with the failed key fob receiver). Spartan Autoworx did the cloning. The clone does have my VIN on it. The scanner originally showed "*" for its status instead of ON or OFF. Once I toggled it the * went away and now it just lists its current state.

Oh and the backup lights aren't working anymore either. Any suggestions on what to try next?

 

the button itself might be dirty if you can trigger it with the scan tool. as for the backup lights maybe you need new ones.

 

I asked Eric at Spartan Autoworx about this. He graciously offered to find me another BCM and flash it with the contents of my original PROM. A week later he had one and shipped it to me. I plugged it in and now the rear defogger works again. Yay! And the right backup light now works. But the left one still doesn't. And when you step on the brake both turn signal indicators come on (but not the actual turn signal lights). I'm like, huh?

So it's pretty clear there was some issue in the first replacement BCM I tried. But the second one from Spartan isn't quite right either. At this point I'd take it to a dealer but I already know what they're going to say: you need a new BCM but they're discontinued so we can't help you. I could try yet another used BCM but it's not clear that would work any better. I sure wish I could track down a NOS BCM. Sigh.

 

Programming a vehicle's Body Control Module (BCM) is a process of using a diagnostic tool to update software, configure features, or initialize a new BCM to match a vehicle's specific options, and this typically requires specialized tools, compatible software, and manufacturer-specific procedures, often performed by a dealer or experienced technician to ensure proper function of vehicle electrical systems.

 

That is true. However, I'm not starting from a new BCM. I'm starting from a clone of my original BCM. All the customizations are contained in a PROM. If you copy the PROM bit for bit onto another matching number BCM, the result is identical to the original.

In any case, the backup lights are a DOT mandated function, not an option that can be programmed on or off. There is no scan tool menu item that says "Enable backup lights" much less "Enable the right backup light but not the left". The rear window defogger is a standard item on the 2009 H3T. There is no scan tool menu item that says "Enable the rear window defogger". And I sure don't imagine there's a feature that says "Turn on both turn signal indicators when the brake pedal is depressed".

Since different replacement BCM's cause different behavior I'm more inclined to suspect the signals they're generating aren't making it off the board. There's a pair of ST Micro TPS9919J SMD dual channel switches on there. If one of them has a stuck pin, it could cause these problems. The question is, do I want to drag my HP 1671D logic analyzer out to the truck to see what's actually going on? Without a schematic or logic diagram?

What we know so far:
Original BCM: Everything works except the radio receiver.
Clone 1: Radio receiver works but rear defogger and backup lights don't work.
Clone 2: Radio receiver works but left backup light doesn't work. And turn signal indicators come on when brake pedal is pressed.

 

It gets weirder. I put the original BCM back in just to see. Now the key fob receiver is working again! And the rear defogger works. And the turn signal indicators don't come on when you step on the brake. But the right rear backup light works and the left one still doesn't. I checked the left side bulb and it's good. I have a schematic for the 2007 H3 but I'm wondering if it's the same as the 2009 because it doesn't even involve the BCM.

 

 

Solved! I gingerly pushed the wires on the BCM's gray connector towards the plug housing and tried putting it into reverse. Both backup lights now come on. And the rear defogger works. And the key fob works. And the TPMS junk all works. Everything works. Finally. And the ultimate irony is that this is with the original BCM. The one that Valley Cadillac told me was defective which is what started off this year long stupidity. Thanks to everyone here for following along.



Both backup lights now work.

 

Nice work. Did you also seal the connector/contacts?