Odd ball BCM window indexing question???
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Melting Slicks
Joined: Apr 2010
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From: On the coast North of SF bay
Odd ball BCM window indexing question???
Been on a quest to finish my 70 Malibu restomod project with a 2014 Camaro SS donor (link below) and I've encountered a major stumbling block. The BCM does not like the after market motors in the newly installed electric regulators for the windows in the Malibu; I can not get them to index and be accepted into the system.
None of the options I'm aware of, while they will probably work, are not pretty and both are very labor intensive.
I have reached out to a service manager for one of our local Chevy dealers, with whom I have a pretty good relationship, and he agreed to email a GM engineer friend and ask the following question:
"What is the value and type of the comparator that the BCM and window controller use for making the determination that the motor is functioning correctly?". The BCM queries the controller and the controller responds with some value and if the value is correct, the BCM says ok we're done, otherwise the BCM sends the value again, and repeats a total of three times. The value comparison is needed because all batteries and charging systems do not operate equally. This makes me think this is totally doable, but here I am.
Seems like a straight forward question but I'm told he never received a reply.
BTW, modifying the BCM to coincide with what the Malibu has now is not in the cards. The internal code in the BCM is tested at startup, and perhaps at other times; it performs a self check and the adds up the numerical values of all the encoded characters and that value needs to match the original sum determined at the factory. Making that kind of change is way above my pay grade...
If you think about it, the "type" needs to be either a voltage drop percentage or a current draw range. I have determined that I can vary either of those to a fairly great extent, but what is the correct variance; both type and value? I'm guessing that it's a voltage drop percentage, probably between 1 and 5 percent.
Now I know there are a lot of techies on this forum and I hope one of you can successfully answer that question.
Appreciate any help on this - many thanks,
Nick
None of the options I'm aware of, while they will probably work, are not pretty and both are very labor intensive.
I have reached out to a service manager for one of our local Chevy dealers, with whom I have a pretty good relationship, and he agreed to email a GM engineer friend and ask the following question:
"What is the value and type of the comparator that the BCM and window controller use for making the determination that the motor is functioning correctly?". The BCM queries the controller and the controller responds with some value and if the value is correct, the BCM says ok we're done, otherwise the BCM sends the value again, and repeats a total of three times. The value comparison is needed because all batteries and charging systems do not operate equally. This makes me think this is totally doable, but here I am.
Seems like a straight forward question but I'm told he never received a reply.
BTW, modifying the BCM to coincide with what the Malibu has now is not in the cards. The internal code in the BCM is tested at startup, and perhaps at other times; it performs a self check and the adds up the numerical values of all the encoded characters and that value needs to match the original sum determined at the factory. Making that kind of change is way above my pay grade...
If you think about it, the "type" needs to be either a voltage drop percentage or a current draw range. I have determined that I can vary either of those to a fairly great extent, but what is the correct variance; both type and value? I'm guessing that it's a voltage drop percentage, probably between 1 and 5 percent.
Now I know there are a lot of techies on this forum and I hope one of you can successfully answer that question.
Appreciate any help on this - many thanks,
Nick
Last edited by pcguy2u; May 8, 2022 at 12:51 PM.
