Theory Of Operation

WARNING: This page is about a different car, the 2024 RAM ProMaster EV. However, it is still accessible from the selected car via links, so may be relevant.

The Body Control Module (BCM) uses a transponder mode to query the key Frequency Operated Button (FOB) for low battery state in keyed ignition systems. This is done after the FOB authentication is complete so that it does not impact the starting system timing. The Low Battery condition determination is the responsibility of the FOB. The BCM receives FOB Battery Low information by two methods: 1) If any FOB has a low battery condition during authentication for the Keyless-Go feature. 2) If any FOB reports a low battery condition within its Remote Keyless Entry (RKE) command to the BCM.

The BCM also monitors the rolling code synchronization with the RKE transceiver FOB. When the FOB is pressed over 1024 times, it loses synchronization with the rolling code. Re-syncing automatically takes place in the background after the vehicle has been started and driven above 5 mph. This happens once per ignition cycle above 5 mph to all FOBs located inside the vehicle, just in case one of the FOBs was de-activated during a FOB safe lock procedure.