What might cause my 2015 VW Passat TDI check engine light to come on?

There are quite a few reasons why the check engine light might be on in Your 2015 VW Passat TDI. The most common cause in nearly all vehicles is a loose or damaged gas cap. Tightening or replacing this part will typically fix the problem. Bad spark plugs, spark plug wires, and ignition coils can trigger the light, as well. Your vehicle has one plug and coil for each cylinder. A failed oxygen sensor is another common cause. This sensor measures unburnt oxygen in the exhauSTSystem. The vehicle will run with a failed sensor, but it can do damage to the catalytic converter and spark plugs, if left unaddressed. Speaking of, issues with the catalytic converter can trigger the light, too. This is generally one of the more expensive repairs associated with the check engine light. You can also have issues with the vacuum, hoses, battery, mass airflow sensor, aftermarket alarm, or exhaust gas recirculation valve.