Whar is safe mode? on 1997 Audi A8 Quattro

My 1997 Audi Quattro went into "safe mode" with all the gears selected and lit up in red on the dash that normally indicates what gear the car is in? No power, but driveable?

Asked by for the 1997 Audi A8 Quattro
Possible short term loss of power - put radio in "safe" mode and caused the engine and trans to go to "limp" mode - causes loss of power and trans stays in upper gears. Question is - what cause the power loss? Have it diagnosed asap.

Keith Cox Autobahn