Meiko UPster U 400 M2 Error Codes ERR 310-312: Tank Temp Sensor

What does MEIKO error code ERR 310 / 311 / 312 mean?

The tank temperature sensor tells the UPster U 400 M2 how hot the wash water is, and the heating is switched on and off from that reading. The control watches the sensor for plausibility. ERR 310 and 311 report that the sensor circuit has shorted or opened, so the reading is not usable. ERR 312 is the one to treat with care: it reports an actual tank temperature above 85C, which can happen when a heating contactor sticks closed and keeps heating the tank. Per the maker, it is not possible to continue in any of the three cases and a technician should be called. The causes are a sensor that has shorted or opened, wiring that is cracked or loose at the plug, a contactor stuck closed, or a control board input that reads the sensor wrongly. Because 312 may mean the tank is really too hot, the first thing to do is switch the machine off with its own key and leave it to cool before anyone reaches in.

Affected models and control systems

This applies to the Meiko UPster U 400 M2 glass and dishwasher. Other Meiko models and controllers use different numbers for temperature 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 310, 311 or 312 on the display
• Tank water that is steaming or very hot
• Heating that does not stop or does not start
• Machine that stops on its own

Possible causes

Listed in MEIKO's documentation

• A tank temperature sensor that has shorted or opened
• Sensor wiring that is cracked or loose at the plug
• A heating contactor that sticks closed and keeps heating the tank
• A control board input that misreads the tank sensor

Other likely causes — what usually sits behind error code ERR 310 / 311 / 312 on this control. A technician confirms which one it is before any part is replaced.

• Sensor cable chafed where it passes the tank edge
• Contactor contacts welded by repeated heavy switching
• Corrosion at the sensor plug from steam

Safe checks before calling for service

How a technician diagnoses error code ERR 310 / 311 / 312

1. Read the error and note which of the three is active.
2. Let the tank cool and isolate power.
3. Measure the sensor resistance and compare with a probe thermometer.
4. Check the plug and wiring.
5. Test the heating contactor for sticking closed.
6. Replace the sensor or contactor only after the tests.

How error code ERR 310 / 311 / 312 differs from similar codes

ERR 304 is the heat-up running too long, while the 310 series is about the sensor circuit or a tank that is too hot.

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.