Thermador Pro-Harmony Range Showing E4 and Light Code 12: Shorted Oven Sensor

What E4 means

Owners of older Professional Series ranges (PDR30/36/48, PRG30/36/48) may see the oven light flash once and the heating light flash twice, repeating. That is code 12, which the legacy service document lists as E4: oven temperature sensor shorted. The control sees an electrical path where none should be, so its temperature reading cannot be trusted. On current Thermador ovens, E4 is a different story.

Usual causes of E4

Oven temperature sensor shorted (sensor or its wiring)

✓ A safe check worth trying

1. Count the flashes: one, then two. 2. Turn the oven off and give it time to cool. 3. Cycle the range breaker off and on once. 4. If the pattern repeats, stop baking and broiling and schedule service; do not open panels to look for the wire yourself.

! Why you should stop here

A shorted circuit may be a pinched lead deep behind the cavity wall.
Meter checks on live range wiring are not for owners.
Our diagnosis comes with a written price before any part is ordered.

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 Range codes

E12Thermador Pro-Harmony Range E12 (Light Code 11) - Expansion Board Not Connected U400Thermador Induction Range Cooktop U400: Supply Voltage Out of Range E13What E13 Means on a Legacy Thermador PDR/PRG Range: Vcc Lift-Off, Code 13 F1 / F6Thermador Induction Range Cooktop F1 / F6: Cooking Zone Overheated E14Thermador Pro-Harmony Range with Five-and-Five Blue Lights: E14 Selector Switch Error F2 / E7015Thermador Induction Range Cooktop F2 / E7015: Electronics Overheated EThermador Range Display Reading "E" Plus a Number F1Thermador ESC30/GSC30 Range F1: Supervisory Relay Enable Shorted

E4E4 questions

How is E4 different from E3 on these ranges?

E3 reads an open sensor circuit and E4 a shorted one. Both mean the control has lost a believable oven temperature, but they point a technician to different checks.

Could a bad sensor make the oven overheat?

The control relies on that reading to regulate heat, so we do not recommend using the oven while the pattern shows. Switch it off and call so we can test the sensor circuit.

Do I need to remove anything before you arrive?

Just take out racks and cookware once the oven is cool. Leave wiring and panels alone; we handle that part when we arrive and explain what we find.