DTC 43: Body Control Module With SUMCHECK Error: Description
WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
A digital Radio Frequency (RF) message received was from a remote transmitter that is programmed to Body Control Module (BCM), but message did not pass sumcheck security test. No remote function capabilities will exist. DTC 43 will set when BCM is in diagnostic mode, any remote transmitter button is pressed and remote transmitter signal does not pass sumcheck security test. Most likely cause is that remote transmitter is out of synchronization.