Bosch Dishwasher (Gaggenau) Showing F2? Diagnosis

What F2 means#

The board runs the flow-through heater and reads water temperature from the NTC thermistor. If the heater is drawing current but the temperature response is wrong — no rise, too fast a rise, or wild swings — the board assumes a dangerous condition (a dry-fire, a runaway heater, or current leaking to ground through water) and trips F2 to stop it before anything is damaged.

What triggers F2#

• No temperature change despite heater current: the NTC may have failed reading a fixed value, the heater may be firing without water contact because of a low fill, or the NTC probe may have slipped out of its mounting and be reading air.
• Temperature rising faster than the heater could explain: often a ground fault in the heater passing current through the water directly — the dangerous case — or an NTC that has developed a low-resistance fault and reports falsely high heat.
• Temperature oscillating wildly: usually a loose NTC connector or a cracked sensor making and breaking contact as it heats.

DIY diagnosis (power off at the breaker)#

1. Test the NTC first. Disconnect its two-pin plug near the heater and measure resistance; expect roughly 4-6k ohms at room temperature. Out of range means replace it.
2. Test the heater. Measure across its terminals; a healthy flow-through heater reads about 10-14 ohms (the same check as E09). A good heater with a bad NTC means replace the sensor only.
3. Check the probe seating. Make sure the NTC is fully pushed into its housing and touching the sump, not dangling in air.
4. Look for leaks and board damage. Water dripping on the heater connections creates ground-fault paths, and carbon tracking on the EGS board's heater relay — dark lines between contacts — leaks current the safety circuit flags.

Worth-fixing verdict#

Replacing the NTC sensor resolves about 65% of F2 cases and is one of the cheapest [dishwasher](/blog/repair-or-replace-dishwasher) parts, so it is almost always worth trying first once testing points there. Replacing the flow-through heater covers about another 20%, an EGS control board about 10%, and corroded connectors the remaining 5%. Because the NTC fix is so cheap and the alternative — a ground-faulting heater — is a genuine safety issue, F2 is worth diagnosing properly rather than living with. Never clear it by repeated resets: if tests suggest a heater ground fault, confirm the element's insulation resistance to ground reads above 1 megohm before trusting the machine again.

Why F2 is not the same as F1 or E02#

It helps to see where F2 sits among the BSH thermal codes. F1 means only the NTC sensor is out of range — a low-severity, operational fault you can often keep using the machine with briefly. E02 means the heater alone is underperforming — a performance problem, not a safety one. F2 is different: it fires when the heater and the sensor disagree at the same time, which is the board's way of saying it can no longer trust either reading enough to heat safely. That is why F2 locks out heating entirely while F1 and E02 are less urgent, and why the diagnosis has to cover both the sensor and the heater rather than just one.

Before you order any part#

Run the two resistance tests first — NTC and heater — and check the probe seating and connectors. That order matters because a healthy heater with a bad NTC is a cheap sensor swap, while replacing the heater or board on a hunch is the expensive way to be wrong. Only move to the heater or the EGS board after the sensor has been ruled out with a meter.

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