From reading posts and looking at YouTube videos I think I can replace the BCM module in the 2004 L300 wagon that my kid is driving. But it seems that if I buy a used BCM or a new one that it may not work and that it may need to be programmed to function, or maybe it will be ok without special programming. Does anyone have any special knowledge on this and advice? Should I have a shop buy and install the device? Should I buy the device (new/refurbished from GM or Rock Auto? Used from eBay? Does it matter?) and take it to a GM dealer to program it and then install it myself? Can I just buy a used one and install it without reprogramming? Any other ideas or recommendations? Also, I saw a video in which a technician removed the BCM and opened it up and looked at the mother board and saw discoloration and warpage - is this a good way to diagnose that the BCM is bad? The symptoms are flickering lights on the dashboard and various warning lights coming on and off and other general electrical weirdness in the interior/dash. Thanks!

 

Sounds consistent with BCM going south.

For the BCM to "function like the original you need
1) the correct BCM hardware (pt number)
2) the bcm must contain or acquire the programming that matches the set of options and configurations of your vehicle (or at least be close)
3) If you want the correct odometer reading displayed, it must be programmed into the bcm at the same time the bcm programmed for everything else

If your odometer still reads correctly, take pictures NOW as it usually goes haywire.

A used or junkyard BCM may be fine but in general, it's something only a GM dealer can help with b c it requires special GM electronic "tools" and access to the GM library of code to flash to the BCM for your exact VIN.
Dealers may force you to buy a BCM through them in order to program it.

Ask a dealer for a firm quote.

If you can find one in a junkyard that is essentially from an IDENTICAL vehicle, it may work with no reprogramming.
You'll just need to synch it w the ignition and PCM with a 30 min Passlock relearn sequence to keep the theft-deterrent system happy

 

Sometimes it's just some corrosion on the plug connectors in the BCM. I'd try unplugging and plugging it back in several times after spraying the connector with some CRC Electrical Contact Cleaner. It's a cheap enough try and MIGHT save you some bucks and headaches.