Bosch cooktop error codes: a pan the glass could not sense, a hot surface, or electronics that ran warm.

Not a fault. The zone is on and finds no pan it can heat — nothing on it, a pan that is not magnetic, or a pan too small for the ring. The zone waits, then shuts off on its own.

1. The magnet test: a refrigerator magnet sticks to the bottom of a pan induction can use. Aluminum, copper, glass and some stainless never register.
2. The pan covers most of the ring — a small pot on the big zone, or a pan with a dished bottom that only touches at the rim, is read as nothing.
3. The pan sits centered on the zone, flat on the glass, with nothing between (a heat diffuser, a trivet).

A magnetic, flat pan on the right-size zone, centered, and the mark goes out as the zone heats. A good pan that still flashes on one zone while it works on another is that zone's generator — a part, a technician's job.

Not a fault. The zone is off and the glass over it is still hot enough to burn; the H stays until it has cooled and drops to a small h as it gets close.

1. Leave it. The mark goes out by itself once the glass is below the hot mark; on an electric cooktop the residual-heat indicator does the same.

Nothing to fix. A zone that ran a long time and never showed H, or a mark that never clears on a cold glass, is a zone sensor fault — a technician's look.

Not a fault. The childproof lock is on — the key symbol shows and the keys do nothing — or the cleaning lock has the panel off for about 30 seconds so the glass can be wiped.

1. The cleaning lock ends on its own after about half a minute; the key symbol stays until it is held off.
2. Press and hold the key symbol (the lock key) for about four seconds until the symbol goes out. On the 800 series the lock can be set to come on by itself every time the cooktop is switched off — that is in the basic settings, and it is turned off there.

The cooktop takes settings again. A lock key that does nothing after four seconds with a dry glass is the touch panel — a technician's part.

The electronics under the glass ran too warm and the cooktop switched the zone off to protect itself — a long high-power cook, a hot pan or a hot oven below with no air getting under the cooktop.

1. Take the pans off and let the cooktop stand off for 10–15 minutes; the mark clears as the electronics cool.
2. The vent slots on the underside are clear — a cooktop installed over a wall oven, or boxed in by a drawer pushed tight under it, cannot breathe. The install sheet gives the air gap the cabinet needs.
3. A spill over the control area or a pot lid resting on the keys while it cooled.

Cool, ventilated, and it cooks again. A cooktop that prints F2 on every long cook with the cabinet open underneath has a cooling fan or a zone generator failing — a part, a technician's job.

Not a fault. The zone ran at the same setting for longer than the safety timer allows (a few hours at a low setting, well under an hour at the top) with nobody touching the keys, so the cooktop switched it off.

1. Touch the zone's key to clear the mark and set the zone again — the timer starts over. A pan boiling dry prints the same mark on some models; lift it and let the glass cool first.

Nothing to fix. For a long simmer, change the setting now and then or use the cooking timer so the cooktop knows someone is there.

The cooktop measured a supply it cannot run on — the two hot legs wired so the control sees the wrong voltage, or a leg missing. It will not heat until the hookup is right.

1. Switch the breaker off and leave it off. Nothing on the cooktop is wrong; the junction box under it is.

A licensed electrician checks the connection at the junction box against the wiring diagram on the underside of the cooktop and corrects it. A cooktop installed inside the last month goes back to its installer first; a wrong hookup that was powered is also a warranty question, so note it on the call.