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BCM EEPROM Goodness or How to add OEM remote start

25663 Views 39 Replies 13 Participants Last post by  pinstripebob
For 2011-2015 Cruzes and 2016 Cruze Limiteds made in the United States and Australia that do not have remote start enabled only.

In my quest to find a way to add factory remote start to my 2011 Cruze, (and my side quest for a cure for a bad case of boredom mixed with inquisitiveness), I took a look at a BCM pulled from a 2014 Cruze with remote start.

The first thing I did was immediately investigate the internals. It didn't take long to find an 8 pin 24C16WT sitting by itself. A quick google search revealed that it was the eeprom I was looking for.

Digging out my recently replaced usb reader and adapter clip, I hooked it up to my Surface Pro and read the chip. Just like the radio silver boxes, it comes out mostly as random gibberish but 3 things are in clear text format:

1) the BCM's serial number
2) the donor car's VIN
3) what appears to be a 4 digit security code

I switched the vin to match that of my car and swapped it out. While the new BCM did trigger the anti-theft start lock out and threw a fit about my TPMS needing to be serviced, my car did not outright reject the "new" unit. I was able to access the setting menu through my radio and immediately I noticed a new setting for Remote Start Auto Heated Seats (sorry, can't remember the section name). Remote start itself did not appear in the appropriate section, but I ignored that as I wasn't 100% certain I had the right hood latch in my Cruze.

The next thing I decided to try was cloning my original BCM's eeprom and see what happened. I made backups of both chips, then flashed my 2011 dump to the 2014. A quick reassemble and the new bcm was plugged back in.

This time the results were a bit different:

1) the reported mileage had changed and now matched what I knew was the current amount
2) the anti-theft lock out did not trigger and I was able to start my car right up
3) it still showed the setting for the remote start heated seats

So while it probably was to be expected that the vehicle's mileage would be stored in the chip, it's interesting that the resistor value for our keys is also stored there and both are able to be transferred over without affecting the options programmed into the BCM at the factory.
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Nicely done.

Things like VIN, Serial Numbers, etc, are almost always stored in a section of the cache that can be rewritten as you please. That is... There's no signature or checksum or anything like that.
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I would try to divvy up the segments in the BCM.

Generally at the end or start of each segment will be some numbers specifying where it is, what the part number is, etc... You can then identify the ones you want to keep and update. It might even specify how big the segment is.
2) Software wise, there aren't segments. It LOOKS like there are, but when you compare reads between units or different reads for the same unit after something was changed you'll see that even in the blank areas there are random changes without an indication of what they relate to. The other issue is that while the vin, serial number and (possible) security code are in clear text everything else is encrypted and comes up as gibberish.
When you program them, It is segment by segment. It may not be obvious, but they are segmented.
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