If the indicator lamp flashes while the Audi Q5 is in motion, the ESP or traction control system (ASR) is intervening.
If the indicator lamp lights up ...
- the ESP may have been switched off with the ESP OFF button, or
- the ESP system may have been switched off for system reasons. In this case, the ESP can be reactivated by switching the ignition off and then on again. If the warning lamp goes out, this means the system is fully functional.
ESP/ ABS fault ! See Owner's Manual
If the indicator lamp 
and the ABS indicator lamp 
light up and the message appears, there is a malfunction in the anti-lock brake system or electronic differential lock. This will also cause an ESP malfunction. The Audi Q5 can still be braked in the normal way (however the ABS control function will be out of action).
and the ABS indicator lamp light up and the message appears, there is a malfunction in the anti-lock brake system or electronic differential lock. This will also cause an ESP malfunction. The Audi Q5 can still be braked in the normal way (however the ABS control function will be out of action).Drive to a qualified workshop without delay and have the fault rectified.
WARNING!
If the brake warning lamp lights up together with the ABS indicator lamp and the ESP indicator lamp, this can mean that the control function of the ABS is not working. As a result the rear wheels can lock relatively easily when braking. This could cause the tail of the Audi Q5 to skid sideways. Drive carefully to the nearest qualified workshop and have the fault rectified.
Note
For more information about the ESP and ABS systems, refer to Link.