Error message : e01 f09

Power supply issue that will sooner or later become permanent.

Yo James,

I know nothing of your unit, but I've never let that stop me before??.

Sounds like a sensor is stuck in the "tray full" position and popping an error message based upon what "it" is detecting.

OK, how does the unit know from "full tray" (what ever that means). I'm a big believer in problems being created by dirt, crud and in your case, coffee grounds. Unless the sensor (switch?) itself has failed, I'll bet there is debris fouling the system.

Find the "full tray" (what ever that means ??) sensing mechanism and clean/replace it and I'll bet you will solve the problem.

All the best.

is it an electric or gas or oil fired. Er3 means it is not getting up to temperature within the required time. Electrical - element bad. for oil or gas, no ignition or fuel supply.

What is model number?

Open following link for rheem tankless resources, including error codes and typical maintenance.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

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

Hello,
Most likely your flame sensor wiring is partially burn't or has an open circuit fault that's giving you the error message. This wire starts at the gas control and ends next to the pilot assembly. It can easily be replaced using a small wrench to unscrew the end connector from the control and the flame sensor rod at the pilot assembly. Call Rheem and see if the water heater is still under warranty, but even if it isn't they can most likely order the part you need for you. The phone # is on one of the data decals on the side of the water heater tank. They will need the model # and serial # to order the part. Be sure you unplug the unit before working on it! Douglas

thats a ignition failure.. Check for Gas to the unit.. or have a qualify technician check it

a 16 error code is typically caused by scale formation. I'd recommend performing a descale on the heater.

4 error message, the 4th (last) error code is #13, not enough oxygen.

Check the location of the heater, if it is fine the ODS sensor (actually is a thermal couple) is bad.

I've installed a number of these units and the C4 76 error code is a bad PCB board. The remote unit is not communicating with the PCB board so you need to call customer service at 800 432 8373. You'll need to give them your name, address, model number and serial number. They'll send you a new PCB board with instructions on how to swap it out. It's pretty easy.
Meanwhile, you might be able to get hot water while you wait the day or two for the replacement parts to arrive by simply disconnecting the wires from the remote at the PCB board. This works about 50% of the time. Once they're disconnected try turning on the hot water full blast and see if the unit fires.
Good luck with it.
Paul (Redwood City, CA.)