Bosch Singular 4000 Service Manual page 51

E4 Error - Wire Check
1. Check the connection of the wire.
Figure 78 Control Board
Figure 79
Pressure Sensor
Singular Combi Boiler - BTC 439002301 A (12.2021)
E4 Error - Pressure Sensor Check
1. Measure the resistance of the Pressure sensor.
2. Check the pressure sensor input voltage at the control board.
Normal: DC 5 V
—
Abnormal: 0 V
—
3. Replace the control board if the voltage output from the control board is
abnormal.
Figure 80
Service Manual
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