Evening folks, my sigma alarm fob battery appears to have finally given up. (1993 E34 520i) Anyone know what’s required to replace the battery ie is it a simple replacement or is it a solder in job. Couldn’t really find much on line about them. The only number on it is MPT 1340, but when you google that it comes up with just about every sigma alarm fob ever made! Any guidance appreciated before I hack it to bits and make an ar5e of it, i’ve heard some of these fobs can be prone to losing ‘memory’ if you don’t complete the battery swap quickly. Thanks!