No Communication to BCM
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Joined: Jan 2018
Posts: 57
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From: Meriden Connecticut
LMC5 Done!
The LMC5 when installed properly will cause the lock motor to be disconnected so that it does NOT have power any longer. There is a video on the install of the LMC5. I suggest watching it to see how to remove pins from the connectors but the video leaves out an important step about disconnecting a specific fuse. READ AND FOLLOW the written instructions that come with the LMC5. They contain ALL the correct steps. Use the video just to see how to deal with the connector pins. 
What the LMC5 is doing is responding to the lock and unlock commands that the BCM is sending to what the BCM thinks is the lock motor. The BCM has no physical way to know if the column is locked or not. It functions on a command-response protocol. It sends a lock or unlock command and expects a response back to know that its command was received and acted upon so that it can keep a "state" bit about the expected condition of the lock. When working as designed the lock motor both operates a lock pin that is intercepted by a lock plate to lock/unlock the column and also sends back a signal to the BCM that the operation was completed. There are several components between the BCM and the lock motor that can fail and result in the commands either not being received by the lock motor or the response not being received back by the BCM. Low battery voltage is the primary cause of the failure of the column lock system as designed. The LMC5 connects right at the BCM so all factory original or recall column lock components after the BCM are abandoned in place but disconnected from the BCM. The LMC5 is simply receiving the lock and unlock commands and responding to them to fool the BCM into thinking the column lock system is functioning correctly. Because it works with very low voltage and is directly connected to the BCM connectors it is hugely more reliable than the original components. So even if the battery is very low the LMC5 will function correctly.. That likely will NOT be the case for most other C5 electronics.
What the LMC5 is doing is responding to the lock and unlock commands that the BCM is sending to what the BCM thinks is the lock motor. The BCM has no physical way to know if the column is locked or not. It functions on a command-response protocol. It sends a lock or unlock command and expects a response back to know that its command was received and acted upon so that it can keep a "state" bit about the expected condition of the lock. When working as designed the lock motor both operates a lock pin that is intercepted by a lock plate to lock/unlock the column and also sends back a signal to the BCM that the operation was completed. There are several components between the BCM and the lock motor that can fail and result in the commands either not being received by the lock motor or the response not being received back by the BCM. Low battery voltage is the primary cause of the failure of the column lock system as designed. The LMC5 connects right at the BCM so all factory original or recall column lock components after the BCM are abandoned in place but disconnected from the BCM. The LMC5 is simply receiving the lock and unlock commands and responding to them to fool the BCM into thinking the column lock system is functioning correctly. Because it works with very low voltage and is directly connected to the BCM connectors it is hugely more reliable than the original components. So even if the battery is very low the LMC5 will function correctly.. That likely will NOT be the case for most other C5 electronics.
