You may be surprised if your 2005 Sprinter’s check engine light is on. If the check engine light is illuminated, there are several things to look for to determine the cause of the problem. The malfunction of the Mass Airflow sensor could be the reason why the check engine light illuminates. The sensor monitors the amount of unburned oxygen in the exhaust fumes and balances the air-to-fuel ratio. If the sensor becomes dirty it can affect engine performance and cause increased emissions.