Freezer beeps and displays E01; temperature may rise slightly and alarm icon may flash.

Safety first: Unplug the freezer from the mains power supply before removing any panels. Do not work on live circuits.

Step-by-step checks:

• Power cycle: Disconnect power for 5–10 minutes, then reconnect. If E01 clears and does not return, it may have been a transient fault.
• Locate the NTC sensor: On many Bosch freezers, the freezer temperature sensor is located behind an interior panel on the rear wall or in the side wall near the evaporator. Remove the drawers and the inner back panel (usually secured by Torx or Phillips screws).
• Inspect wiring: Check the sensor wiring harness from the sensor to the top or rear where it connects to the main control module. Look for cuts, pinched wires, or corrosion at the connectors.
• Test the sensor: With the unit unplugged, disconnect the NTC sensor from the harness. Use a multimeter set to resistance (kΩ). At room temperature (~20°C), most Bosch NTC sensors read roughly 4–6 kΩ (check service data if available). If it reads open (OL) or near 0 Ω, the sensor is faulty.
• Replace the sensor: If the readings are out of range, install a new Bosch-compatible freezer NTC sensor. Route the new sensor along the original path and secure it away from moving parts or sharp edges.
• Check the control board: If the sensor tests good and the wiring is intact, the main control module may not be interpreting the signal correctly. Inspect the board (usually located in a housing at the top or rear) for burn marks or damaged components. Replacement of the control module is typically required if it is found to be faulty.

When to call a technician: If you are not comfortable testing resistance or accessing the control board, or if E01 persists after sensor replacement, contact a Bosch-authorized service technician.