Faulty Idle Air Control (IAC) valve
Idle Air Control (IAC) valve harness is open or shorted
Idle Air Control (IAC) valve circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
Idle System Learned Value Upper Limit Attained is the generic description for the P1508 Audi code, but the manufacturer may have a different description for your model and year vehicle. Currently, we have no further information
about the P1508 Audi OBDII code.