2008 Mercedes SL-Class Owner's Manual - Page 306

Operation Tires and wheels If you wish to confirm activation: Press button æ. The following message will appear in the multifunction display: Run Flat Indicator Restarted Checking tire pressure electronically with the Tire Pressure Monitoring System (TPMS), (USA only) i This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation. Any unauthorized modification to this device could void the user's authority to operate the equipment. i The Tire Pressure Monitoring System (TPMS) is equipped with a combination low tire pressure/TPMS malfunction telltale in the instrument cluster ( page 29). Depending on how the telltale illuminates, it indicates a low tire pressure condition or a malfunction in the TPMS system itself: If the telltale illuminates continuously, one or more of your tires is significantly under-inflated. There is no malfunction in the TPMS. If the telltale flashes for 60 seconds and then stays illuminated, the TPMS system itself is not operating properly. After a certain "learning phase", the Run Flat Indicator checks the set pressure values for all four tires. If you wish to cancel activation: Press button ç. 305