Machine displays ER03 and will not complete warm-up

Safety: Unplug the machine and allow it to cool fully. Steam boilers can retain pressure and heat for a long time.

• Power cycle: After cooling, plug in and power on. If ER03 appears immediately, the control board is not reading the steam boiler sensor correctly.
• Check for descaling needs: Heavy scale can cause abnormal temperature readings. If the machine will allow, run a full descale cycle with Sage-approved descaler. However, ER03 usually indicates an electrical sensor issue rather than pure scale.
• Internal inspection (advanced):
  • Remove the top/back cover to access the steam boiler.
  • Locate the steam boiler thermistor (usually clipped to the boiler body) and follow its wires to the PCB.
  • Check for loose connectors, corrosion, or broken wires.
• Repair: Replace the steam boiler temperature sensor / thermistor harness if damaged. Ensure it is firmly attached to the boiler surface with the correct clip or thermal compound as originally installed.
• Professional service: If the sensor and wiring are intact, the main PCB may be faulty. This requires board-level diagnosis and should be handled by a qualified technician.