Could anyone tell me what the following dash light might mean please? It's a yellow anti clockwise arrow with a triangle and an exclamation mark in the centre. It first appeared about 2 months ago and has only shown itself another 2 times up until the beginning of this week. It now comes on almost every trip after about 20 minutes of driving. The lamp resets after the the engine is switched off and back on. No noticeable change in anything when the lamp appears. The car is a 2002 A4 Avant 1.9TDi Any ideas?