Thermador Oven F40 on Older C-Series Models: Upper Meat Probe Shorted

What F40 means

F40 on an older Thermador C, CM or CJ oven says the upper oven's meat probe circuit reads as shorted. The service document points at a short in the probe wiring and says to check header P2 on the control display board and make sure the probe wire is not pinched. It is rated low severity, since normal baking without the probe may be unaffected. Newer Thermador ovens can use F40 differently.

Usual causes of F40

Short circuit in the meat probe wiring
Probe wire pinched, for example in the oven door or jack area
Control display board, replaced if the code persists

✓ A safe check worth trying

1. Stop using the meat probe and leave it out of the oven. 2. Switch the oven off at OFF or the breaker and wait three minutes. 3. Restore power and bake without the probe. 4. If F40 returns, note whether it appears with or without a probe inserted, and call us.

! Why you should stop here

The probe, its jack and header P2 are separate suspects
A pinched wire can look fine from outside
We quote in writing first, with legacy parts confirmed by model number

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

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F40F40 questions

Does F40 stop the oven from baking?

It is rated low severity because the probe is an accessory circuit. Many owners can bake normally without it, but we still recommend a check if the code returns or other trouble appears.

Is it the probe or the oven?

Either can cause it. The source lists wiring, header P2 and the display board. Telling us whether F40 appears with the probe removed helps us narrow it down.

Can I buy a replacement probe myself?

A new probe may help only if the old one was the problem. We prefer to test first, since a pinched wire or board input could leave F40 on the display.