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Error code reference
Bosch Water Heater Error Code E9
Overheat sensor (ECO) open circuit (resets when cooler temperatures are detected 220°F/104°C).
SourceBosch GWH 715 ES - Service Manual: Installation, Operation & Maintenancep. 40
Diagnostic procedure
The full E9 procedure
Step 1 is visible so you can confirm you are on the right page. The remaining steps, the ones that tell you whether to actually replace a part, unlock with any pass.
MyPros+ · DiagnosticsStep 1 preview
1
First diagnostic step
Disconnect power supply cord and check wire connections on overheat sensor (top right of heat exchanger) and the two connectors on the control board.
SourceBosch GWH 715 ES - Service Manual: Installation, Operation & Maintenancep. 40
More steps, wiring diagram references, and verified part numbers
Includes expected resistance and voltage values, connector pinouts, and supersession notes for replacement parts.
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Where this code is documented
1 manual in the MyPros+ library documents this code for Bosch water heater.
Models covered by the manuals that document this code
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