Legacy Thermador CT/CMT Wall Oven Showing E4: Shorted Temperature Sensor

What E4 means

Seeing E4 on an older Thermador CT or CMT oven with a Dreefs control means the temperature sensor is reading as shorted, with resistance below 5000 ohms, the opposite of the open reading that E3 reports. The oven cannot trust its own temperature, so heat is switched off in the failed oven only. The message can be canceled once a good sensor is detected. The source action says to check the sensor.

Usual causes of E4

Shorted oven temperature sensor
Sensor wire pinched or touching metal along its run
Control board input misreading the sensor signal

✓ A safe check worth trying

1. Switch the selector to OFF, and a slight counterclockwise tweak should settle the display. 2. Let the oven cool completely. 3. Try the other oven cavity if your unit has two. 4. If E4 reappears on the affected oven, keep it off at the breaker and book a service visit.

! Why you should stop here

Telling a shorted sensor from a pinched wire means pulling the oven and testing it
Bypassing a sensor is unsafe because the oven would run with no temperature control
We confirm the exact legacy part by model number and quote in writing before work

Taking off a panel yourself does not by default void a manufacturer warranty, yet it can lead to accidental damage, and some manufacturers attach their own service terms. Read your warranty paperwork, or ask us, before you decide.

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More Oven codes

F14Thermador Older C-Series Oven, Control Display EEPROM Error F14 F52Thermador Wall Oven F52 in the Legacy C/CM Family: Upper Door Reads Locked and Open F3Thermador Wall Oven F3 in the Legacy SC/SM Family: Open Oven Sensor F19Thermador Oven F19 (C/CM/CJ Legacy Models): Miscellaneous Power/Relay Board Error F53What F53 Means on a Legacy Thermador C/CM Wall Oven: Upper Door Stuck Locked F4What F4 Means on a Legacy Thermador SC/SM Wall Oven: Shorted Oven Sensor or Under 40 F F20F20 on Thermador C-Series Upper Ovens: CANCEL Key Shorted High F54Upper Latch Input Shorted: Thermador Wall Oven F54, C/CM-Series Legacy

E4E4 questions

What is the difference between E3 and E4?

E3 is an open sensor reading above 5000 ohms. E4 is a shorted reading below 5000 ohms. Both stop heat on the affected oven, and both point the technician toward the sensor, its wiring or the board.

Is it safe to leave the oven plugged in with E4 showing?

The heat is already off for that oven, so the display itself is not a danger. We still suggest switching it off at the breaker if it keeps flashing, and having it checked soon.

Will the other oven still bake?

The source says the failed oven alone loses heat. A second oven or microwave section on the same unit should stay usable, though we recommend a full inspection of the whole cabinet.