I'm not a gambling man but I would risk a shilling that the radiator fan is running Peugeot fans are not ignition controlled, and do start at times after the engine is switched off.
Because on the 206 the radio is always able to get battery power supply voltage.
It is probably your cooling fans. These are electric and may run with the engine turned off. It is probably your cooling fans. These are electric and may run with the engine turned off.
The frist thing I would check would be the engine mounts.
GASOLINE ENGINE OR DIESEL?
I am not sure as to what sound the noise is making but if it sounds like the engine is still funning after the car has been turned off it is the fan. Depending on what temp the engine is and the temp outside, the fan could run if its too hot.
Probably answered by this service bulletin: TT0404-004 APR 04 Body - Whistle from Engine Area
turn the engine off
My roof A/C stop working for a little bit, we turned it off to avoid damages but we couldn't stand the heat and turned it on again after 5 minutes. Now the engine is making an audible noise.
There are pages and pages and items that can cause a check engine light. You need to have it checked for codes with a scan tool. After repair light can be shut off with scan tool.
When a check engine light comes on, it means that there are issues with the engine. It gets turned off when the person resolves the problem that caused it to turn on.
It sounds like your ignition timing timing is too far advanced. It will need resetting.
Gasoline engine - spark is cut off when ignition is turned off Diesel engine- fuel is cut off when engine is shut down