On your 300E cnetrol locking system should
work at all three locks (two front door & trunk)
I will try to reset the centrol locking pump
The pump is under your rear seat cushion at
right side,Just disconnect power supply to
pump (black plastic connector) for prox 15
second then reconnet it back to pump.
Then try to operate lock from L/front door.
If not working you should have a wireing problem.