2004 Mercedes SL-Class Owner's Manual - Page 214

Controls in detail Driving systems Parktronic malfunction There is a malfunction in the Parktronic system if the red segments of the Parktronic system warning indicator come on and a warning sounds. The Parktronic system will switch itself off after 30 seconds and the indicator lamp on the Parktronic switch comes on. Have the Parktronic system checked by an authorized Mercedes-Benz Center as soon as possible. If only the red segments of the Parktronic system warning indicator come on and no warning sounds, then the sensors of the Parktronic system are dirty or malfunctioning. Malfunction may also be caused by interference from other radio or ultrasonic signals. The Parktronic system will switch off after 20 seconds. Clean Parktronic system sensors ( page 277). Switch on ignition. or Check Parktronic system operation at another location to rule out interference from outside radio or ultrasonic signals. 213