Key fob unlocking

My 2000 SL500 has recently developed an intermittent issue (now more often that not) where you can lock the car with the key fob but you can't unlock it. The lights flash when you press unlock so the key is transmitting and the IR receiver is receiving. And you can lock/unlock everything with the key in the door or the trunk, so it is not the vacuum pump module itself.

I think the issue may be a bad connection between the IR remote module and the lock/unlock line on the vacuum pump. Does anyone know where the remote module is located on a 2000 so I can inspect the connections?

Thanks!