This little book presents background information on the exhaust gas scandal, e.g. which pollutants are critical, how engine control units, exhaust gas recirculation and exhaust gas aftertreatment work, which driving cycles are used for testing, how manipulations on the test bench are possible and in which legal and political environment this could happen unnoticed for a long time with different consequences in the EU and the USA. Measures are presented with which vehicles can also comply with real legal limits and how manipulations can be prevented legally and politically in the future. Additional details are made accessible to the reader through references to literature.