Just the middle section with the mileage display is very dull and can hardly be seen. i've checked the manufacture book but no

The bulb is gone - you need to take the instruments out to replace it.

some cars have their instrumentation run off lithium batteries located on the rear of the display panel and with all batterys they eventually die. they are just like big watch batteries soldered in the panel. l had this on my bmw apparently its a common fault good news is its very cheap to fix. hope this helps

Just a bulb (could be 2). These are available very cheaply from your dealer - they are tiny little things. The are a push and twist fit BUT depending upon your year, some of the displays did not have replacable bulbs and with those you have to replace the display unit.