Meiko UPster U 400 M2 Error Code ERR 307: Level Sensor Defective

What does MEIKO error code ERR 307 mean?

Safe operation depends on the machine knowing how much water is in the tank. The UPster U 400 M2 reads this through a tank level sensor and its sensing tube. ERR 307 is the control's report that the sensor is defective: the signal is missing, out of range or otherwise not believable. Without a level reading the control cannot fill, heat or drain safely, so it stops and asks for a technician. The manual treats it as something staff cannot clear. Nothing at the operator level can be adjusted or cleaned to remove it. The sensor itself may have failed, the tube leading to the tank may be pinched or loose, a wire between the sensor and the control board may be broken, or the board input may be reading the signal wrongly. A restart sometimes clears a one-time glitch, but a repeat means a part needs testing. Panels should stay closed, because the sensor and board sit next to live wiring.

Affected models and control systems

This is for the Meiko UPster U 400 M2 glass and dishwasher. Other Meiko models and other controller generations use different numbers for sensor errors.

Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.

What you may notice

• ERR 307 on the display
• Machine that will not fill or start
• Tank level that cannot be controlled

Possible causes

Listed in MEIKO's documentation

• A tank level sensor that has failed in the UPster
• A pinched or loose sensor tube leading to the tank
• A broken wire between the level sensor and control board
• A control board input that misreads the level signal

Other likely causes — what usually sits behind error code ERR 307 on this control. A technician confirms which one it is before any part is replaced.

• Sensing tube that has slipped off its fitting after the machine was moved
• Moisture in the sensor connector from steam

Safe checks before calling for service

How a technician diagnoses error code ERR 307

1. Read ERR 307 and any earlier level errors.
2. Check the sensing tube for pinching, leaks and secure fittings.
3. Inspect the sensor connector and wiring.
4. Measure the sensor signal against the real tank level.
5. Check the board input.
6. Replace the sensor, tube or board only after the tests.

How error code ERR 307 differs from similar codes

ERR 306 is water above the maximum level, while ERR 307 says the sensor that measures it is itself not working.

Technical reference

Document

UPster U 400 M2 Original operating instructions 9760441 (update 2026-06), 9.6.1 Messages p.33-35

Edition

9760441 / Valid from: 2018-02 / Update: 2026-06

Models / control

UPster U 400 M2

Section

9.6.1 Messages: INFO table printed p. 33, ERR table pp. 34-35 (of 50)

Checked

October 2026

We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.