My tankless water heater Rheem, suddenly stopped working. I do not smell any gas, & remote control shows P1, What I should do ? Thank you.

Might be able to help. Except L1 does not show on any error code file.
Copy following link for Rheem Richmond Ecosense etc computer water heater troubleshoot resources
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
Are you sure the error is not IL? Delime tankless.
Or UL flashes and indicates reset.
Or CL flashes and indicates fault history is cleared.
Or error 11 combustion failure? Call for service.
Or P1? Low water pressure, clean water filter check for leaks and crossover caused by bad single-handled faucet cartridge.
I recommend calling Rheem to find local technician who is qualified to work on tankless computers. Tankless are not ordinary water heaters, and they require continual maintenance to avoid common error codes, especially as unit gets 2-3 years old, after warranty has expired.
The required maintenance and expense of repairs, and general fact that people cannot make their own repairs, make tankless computers a bad choice for heating water.
If unit is 4-5 years old, it might be best to install tank-type heater for $385 from Lowes and cut losses.
http://waterheatertimer.org/How-to-install-gas-water-heater.html
Gene
h

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

Copy following link for troubleshoot resources Rheem/Paloma tankless:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
http://waterheatertimer.org/images/Rheem-service-valves.jpg
http://waterheatertimer.org/Crossover.html

Error P1 is not enough water flow.
Clean water filter located on cold water inlet at top of cold pipe when cold enters unit
Test single handle faucets for crossover
Check if faucet can fill 1 gallon can in 30 seconds.

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

Yes.
Default temperature will be 120 degrees F
Of course the tankless still needs to be plugged into a wall outlet.
Copy following link:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html#remote

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

P1 error code is not enough water flow to operate the unit: increase water flow to unit.
http://waterheatertimer.org/pdf/Rheem-Error-code-P1.pdf
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Error codes are considered start-point for troubleshooting.
Page 18 of maintenance manual shows how to clean water filter monthly.
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf

Other causes can include faulty sensor, clogged in-line filter, clogged water softener, sediment in pipe, sediment at elbow, bad check valve, water leak, etc.

Take a moment and rate answer:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
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Before calling service technician, open following link for Rheem troubleshooting resources:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

C2 11 is: "inadequate gas.
Open the gas shutoff valve all the way"

Another source for error 11 shows: "no ignition"
"Ensure you have gas to the appliance.
Ensure gas type and pressure are correct.
Bleed all air from gas lines.
Ensure gas line, meter, and regulator are sized properly.
Ensure appliance is properly grounded.
Check gas solenoid valves for open or short circuits.
Ensure igniter is operational.
Check igniter wiring harness for damage."

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just clean shower head or faucet with CLR to increase water flow. I have same problem

P1 is reportedly defective check valve that can cause water flow to decrease, and tankless not heat water smoothly. But can also be other causes, or combination of causes. Call service technician, contact Rheem, or replace check valve and see if problem solves. Then add a comment with solution so others can benefit from your experience.

Open following link for Rheem/Paloma/Richmond/Ruud tankless troubleshoot resources including error codes, self help, manuals, parts links, tips, and contact information.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Also take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

1) I cannot find Rheem error code P1
http://www.palomatankless.com/owners/homeowner+trouble.lasso
http://www.palomastore.com/paloma_error_codes.html

2) BOSCH does not show P1 either:
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/2400ESTechSupport/Troubleshooting/tabid/1295/Default.aspx

3) Best I could find is that folks with P1 error code report tankless fires for short period, and then turns off.
This implies air, fuel or vent problem, and can be internal, external or combination.

4) P1 appears frequently on control board descriptors, which might imply the error is control board malfunction.

5) Call Rheem 1-800-432-8373, and then add a comment to this thread and let folks know what you discover.

6) I will also call Rheem when time permits, and post what I discover.

Add a comment for more free help.
Also take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Use following link for Rheem/Paloma/Richmond/Ruud tankless troubleshoot:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

http://www.palomastore.com/paloma_error_codes.html
Range of problems can vary from fan motor wiring, to remote control terminals (error 76), to bad remote, to bad circuit board.
1) Replace remote control
2) Read error 76 and 79 shown in link above
3) Contact local service technician
4) Contact Rheem

Add a comment for more free help.
Also take advantage of fixya expert assistance live.
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Fixya is always less expensive than a service call.

Water inlet temperature to the heater is the same as preset on the controller.
I had this happen to me becouse I have a solar tank with temp of
135 farenheit.
Once I bypassed the sollar tank..no problem