Eternity repair manual - Rheem Tankless Hot Water Heater Rtg-74pvp-2 7.4 Gpm

After a year of trying to correct the problems, Grand Hall, the parent company of Eternal Water Heaters, ceased operations in North America leaving their customers without warranty coverage, part replacements and technical resources
Unfortunately you may have to replace it.

No one can tell you without inspection unit. I found this link with the same problem, have a look



https://www.youtube.com/watch?v=cWmkeyw_hsU



..

if unit had low pressure possible overheat check high limits

normally a small brass gauze filter on the inlet side of the heater inside the pipe

Example of service companies, since you didn't specify manufacturer and model of hot water system:

https://www.servicecentral.com.au/plumbing/repair-of-chromagen-eternity-g20-hot-water-system/406754/

If the thermostat is not functioning properly the heater will run "wide open" and overheat.

http://waterheatertimer.org/Low-hot-water-pressure.html
Link above have general troubleshoot steps to determine possible causes of low pressure

Gene

Water Heater Timers Save Money

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

I cannot find what e11 means but it seems most people have just unplugged it an it came back on. Code goes away.

Is this new installation? Or old installation that stopped working?
Here's the 100% solution. And it applies to all brands, models, types, of tankless water heater, no matter which error code:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html
People should avoid complicated water heaters that claim 'energy star' and '98% efficiency' while proclaiming 'endless hot water' as if the laws of physics, economics and common sense can suddenly be suspended if only the customer would buy expensive, complicated water heater that cannot be maintained or repaired by customer, and there are no qualified technicians who live in your area.
Otherwise you need a service manual, or contact eternal manufacturer. 1-866-946-1096
http://eternalwaterheater.com/pdf/downloads/GU100.pdf
Error E02 does not show in manual.
E2 is ignition failure, which on other brands can be failed PC board... and inadequate incoming air supply, or venting, or failed sensor, dirty combustion parts, air or water in gas line, low gas pressure, wrong gas, etc, or multiples from list above.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

What does it mean when the Eternal tankless water heater reads a SA.06 code when you press "diagnosis" button on the front???? We only get about a minute of hot water and then it goes cold. Customer service 24/7 phone # 1-866-946-1096 is OUT OF SERVICE!!!