My Cadillac CTS was left on accessory and now my battery is dead, it wont start with a jump. What can I do ? No problems prior to this with anything.

If you are trying to start vehicle as soon as cables are connected vehicle will not start because battery is to low leave cables connected for about 3-5 minutes so that battery can be charged also would help to slightly raise RPMS from vehicle jumping your vehicle this will help charge your battery.

Also have a CTS, even if accessory is off but car hasn't been driven for weeks an old battery may not start especially if it is 32F or below where you loose 20% since the computers are always on but in sleep mode. If you do use the car weekly then and the accessory or headlights were on the battery will be drained. If using a battery charger set to 2Amps and wait a few hours. 10A setting can warp the battery plates. If in a hurry and jump starting it should work after a few minutes and the person jumping the car rev's it up for more power. Note: A good quality batter like Duralast, Interstate will work up to 5 to 5.5 years, Walmart Battery Everstart 3 1/3 to 4 years. Check your receipts or log book as to when you got the last battery. n