DTC 43: Last Transmitter Message Received Had SUMCHECK Error: Description

The digital RF message received was from a remote keyless entry system transmitter that is programmed to BCM, but message did not pass sumcheck security test. No remote function capabilities will exist.

DTC 43 will set when remote keyless entry system transmitter is out of sync with BCM. Fault may be caused by transmitter buttons being pressed more than 256 times while out of range of BCM. Fault may also be caused by transmitter battery being changed and buttons being pressed more than 10 times while out of range of BCM. Fault may also be present if digital RF message has an error due to outside noise from surrounding environment, or if transmitter is defective.

Most likely cause is that remote keyless entry system transmitter is out of sync. To resync transmitter, press LOCK and UNLOCK buttons on transmitter simultaneously for 5 seconds.