Q&A

Gas vapors from the fuel tank are stored in a canister (rather than allow these pollutants to be vented to the atmosphere) under certain engine running conditions these gasses are drawn into the engine where they are burned. The evaporative emission system can set a code foe many reasons and needs to be properly diagnosed before just replacing parts. The system is diagnosed using "smoke" or vacuum and a scan tool can open and close solenoids to check their operation. Not sure with Mercedes but speed sensor codes are a sensor on the transmission used to operate the speedometer, cruise control, traction control and or transmission controls.