When the burners ignite, within one minute it starts making a loud banging noise and then the HS code comes on and it shuts down. the noise continues for about 15 to 30 seconds after the burners shut down,

This sounds like a low water flow situation. The heater is telling you that the high limit sensor is curring heater operation. The noises are the heat exchangers boiling the water either due to a blockage in the exchanger , a bad mixing vlve, or most likely poor water flow. This is tough to troubleshoot through a posting like this, but 1st thing is 1st. Check your water flow and make sure it is minimum 50 Gallons per minute.