Automatic gear light blinking on the dash board

Need to get it scanned to see what fault codes are showing .

Please how many litres of gear oil does peugeot 406 uses? My mechanic said it uses 13litres

My Peugeot 406, when about driving or slow down at an instance it won't enter gear but after a while it enters, at process of driving the whole car will be shecking and the two gear light at the datch board will blinking smaltenoeusly the same time.