The battery will measure 12.6 volts if it's fully-charged. If it's at 12.2 volts, it's good but discharged. That isn't sufficient for cranking the engine but the head lights and dash lights would still work. Jump-starting would have worked too unless there was a poor connection on one of the cable clamps.
The most common cause of everything being dead is a bad battery wire connection. Follow the smaller positive battery wire to the under-hood fuse box. Be sure that connection is clean and tight. Follow the smaller negative battery wire to the body and be sure that one isn't rusty or loose. If that one goes under the battery tray, look for other corroded ground wires in that area too.
Monday, October 13th, 2014 AT 4:42 PM