When the battery gets low the alarm system activates causing hazards to flash. The alarm senses voltage drop to detect entry, it also sounds as if your siren is unplugged. There is an alarm siren under the engine hood left side by the fire wall. Test the battery and make sure it is not a high amp battery; the charging system may not have enough output to restore full charge. If the car has an aftermarket radio or other devices that trickle drain the battery over time, consider removing them.
The trouble codes are normally when the check engine light is on or blinking. On means the issue passed, but the code is still in memory. If the light is blinking, the error state is active or current. Having codes without the light may be unreliable information.