HELP! I replaced the BCM in my 2008 Saturn Aura with a Used BCM. I then took it to the dealership to have them program it. Now I notice that my odometer isn't working, so I looked at my invoice from the dealership and it reads the same odometer mileage as my car does and it is 3 weeks later. So, I called the dealership and they stated that they cannot set the mileage to match on a used BCM, that I would have to buy a new BCM? That makes no sense to me. If all the other programming worked to link the used BCM to my VIN number, why wouldn't the mileage be able to programmed as well?
The dealer is correct - what people normally do in this sort of situation is to keep the invoice to prove the existing current mileage and then add whatever gets recorded on the new BCM to give the "real"total for the vehicle.
When you fit a second hand one with a different mileage - it then gets complicated... and people start to get curious or suspicious with "we had a new second-hand unit" fitted and the mileage was X, and the "new second-hand unit" was Y and since then we have done Z so the total mileage is now that reading minus Y plus X with Z already included. They then think TAXI !!! it's been round the clock twice...
While its true the dealer does not correct the mileage on this era BCM, there are many aftermarket solutions to have it done. The best place to look would be a local instrument cluster repair shop. They will likely have the tools needed. If nothing local then it is a common service offered for mail in company's.
On a side note, some of the newer gm bcm's (used or new) will automatically be corrected when programming with GM's SPS software, maybe even most of them since around 2012.