BCM had to be replaced and programmed in my 2003 Saturn LW300 because dash symbols and car inside/outside lights kept flashing on and off. Key fob was re-programmed but it will not accept the new BCM programming. Also, security dash light continues to flash but light does go out when driving car. Does anyone know if anything more can be done to key fob so that I can use it again to open and lock car doors? Since BCM was replaced I have to manually open/lock doors and trunk but I'm willing to put up with this because I really like my Saturn wagon. I know I will have to buy a new car sometime but I want to hold onto my 2003 wagon as long as I can. Just wondering if what I experience with replaced BCM is "normal" or not.

 

How are you trying to program the fob?

There is a possibility that there is a communication issue between the Remote Keyless Entry (RKE) module in the vehicle (which is physically separate from the BCM) and the replacement BCM. Don't know how to test the RKE module to see if it's receiving the fob signal and also successfully sending info to the BCM. I believe that is data that is exchanged as Class II serial (?) network data.

Is the BCM a junkyard pull, or from a different L car or with different options, and if non matching your ride, was it flashed to match?
If it wasn't flashed with the correct firmware to match your model and to cover the option set you have in the vehicle, all bets may be off as to what works and what doesn't when the smoke clears.

 

Don't know how mechanic programmed the fob. Replacement BCM is a junkyard pull from same model as my car. Everything works except the fob so maybe there is a communication issue between the RKE module in my car and replacement BCM. Not much of a hassle to manually lock car so guess I will put up with it. Thanks for your response, Derf. Your answers are always helpful.

 

Np. I try.

Andy may know more about this and has background documentation on the lw300 so he may be able to shed more technical light on the issue,

Another possible straightforward speculation:

If the BCM came from a vehicle without RKE (don't know if that was an option back then or standard), and the mechanic flashed the replacement BCM with a program that does not support rke functionality, this would stop the BCM dead in its tracks from responding to requests from the rke module. RKE requests that are sent to the BCM would then be ignored.

Speculation speculation speculation.

Again Andy may be able to assist you further. I am already past the limits of my L car knowledge, and speculation is not necessarily helpful in situations like this. So I will shut up.

 

 

I did some casual post mortem webs searches which strongly imply that putting in a replacement BCM will cause the fobs to stop working.
They must be re-linked / synced to the vehicle -- through the BCM.

Consensus is that only GM can do this.
Consensus is that it can be done using GM Tech II service device

Supposedly, independent mechanics can get them but the licensing fees and subscription costs to the firmware updates are $$$.

Also, there are Tech II clones that cost around $300 for the brick, cables, adapters, memory cards, and software (which is PC based). Didn't read closely enough to see how/if you get the hex files to download for each car or if you have to find hem yourself. Can't imagine GM would license those files out.

Ultimately, it should cost no more than about $75 to have all of your fobs synched with the replacement BCM, up to a total of 4 for that price. Some dealers do it for free. If you purchased a GM vehicle besides the Satty, try that dealership/
Might want to consider slpurging on an aftermarket replacement remote. The cases crack eventually (1997 in my case) . This way you'll never have to pay to get one programmed when the original bites the dust.

 

Ok. Thanks, Derf.

 

Thanks, Andy.

 

Thanks, Derf. Good ideas. BTW, in my area dealers don't do anything for free here My husband doesn't want to get aftermarket replacement remote. Will put up with locking doors manually. No big deal.

 

Keep in mind that the alarm system is not being set unless you lock the vehicle with the fob.
I only suggested the aftermarket fob as a backup. You can get the existing one reprogrammed just fine.