Battery good -won't jump start - anti theft alarm sounded
1995 avalon xls, appears to have factory installed anti theft system. Battery dies about every five days and requires a boost to start. Has had ongoing battery dying issues since I got it used, but always would start with a boost. Today tried to jump start it, horn sounded- likely from anti theft system. When key is inserted, dash lights come on but engine won't attempt to turn over. Block heater plugged in all night, ran fine five days ago. Nothing in manual about how to disable anti theft system and car won't jump start. Minus 15F out there today so didn't spend much time looking for dead fuses under the hood - any ideas if anti theft is causing starting problem or if maybe this is a fuse or how to disable anti theft system?