Puma parking heater issue

The symptoms do suggest an issue within the auxiliary heating system. Before jumping to conclusions, have you checked the basics, such as the vehicle's battery voltage and the condition of the relevant fuses? A weak battery or a blown fuse can sometimes mimic more complex problems within the ventilation system or blower motor circuits.

I checked the fuses, and they seem fine. The battery voltage appears normal too. You mentioned 'more complex problems' - could a defective temperature sensor cause this?

While a malfunctioning temperature sensor might influence the overall performance of the climate control, it is less likely to be the root cause of a complete parking heater failure, especially when coupled with a stored error code. Given your initial assessment and the persistent error, a defective glow plug within the auxiliary heater unit is a highly probable cause. It might be time for a workshop visit for diagnostics.

Thanks for the help. Took it to the shop, and you were right. Defective glow plug. Repair cost was 440€, and now the auxiliary heater works again.