E4 error code - Bosch AquaStar 2400ES-NG

An E4 error code on your 45 model tankless water heater, indicates that there is an issue involving the flow meter sensor (also referred to as cold water temperature sensor.) This means that the flow meter is not sending a signal to the computer which starts the machine.

Possible broken wire, poor connection or faulty sensor.

Here is a link to all the Noritz error codes. There is NO Code 67. https://inspectapedia.com/heat/Noritz-NCC199-Error-Codes.pdf

I have a model yf-008 110 v 3000w tankless water heater it shows e4 what dose that mean

Call a engineer

1) Copy following links for Rheem tankless error codes
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
http://waterheatertimer.org/pdf/Tankless-Error-code-13.pdf

2) Maintain water heater as shown in product manual to avoid common error codes.

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Error code 36 does not show in Rheem tankless manuals.

Copy following link for general troubleshoot and error codes, and Rheem contact information:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Error code 36 does not show in any resource, including 2008 service manual, or 2012 product manual.
Check that remote control display is illustrating the correct number.
For example there is error code 35.

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

Before calling service tech, open following links for Rheem troubleshoot resources including rheem chat, error codes, possible maintenance and service manual.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Error codes are considered start-point for troubleshooting.
Multiple error codes can mean PC board failure.
http://waterheatertimer.org/pdf/Rheem-error-code-C7-76.pdf
http://waterheatertimer.org/pdf/Error-code-13.pdf
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf

Error codes F1 and F2 do not show among common error codes.
Call Bosch 1-800-642-3111

Before calling service technician, open following links for Bosch troubleshoot resources:
Error codes are considered start-point for troubleshoot.
Multiple error codes can indicate PC board failure.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/250SXOTechSupport/Troubleshoot/tabid/569/Default.aspx
http://forms.boschhotwater.com/Home/BoschTechSupportForm/tabid/614/Default.aspx
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/250SXOTechSupport/ServiceBulletins/tabid/573/Default.aspx

Before calling service technician, open following link for Bosch troubleshooting resources:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Error codes are starting point for troubleshooting, and solutions vary by model and unit.
E4 is Backflow temperature sensor over 309 degrees F. Appliance will close burner and lock.
Check combustion air and backflow vent piping for blockage.
Check if secondary fan connections are disconnected.
Check venting specifications are met. Long vent lengths, venting with more than three elbows, blocked vent or combination venting may cause this failure.
Check sensor resistance

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Look at the manual to see what code E4 is