Mercedes-Benz Automobile Service Manual page 13

d. The operation of the emission control system must
not be altered in any way. Alterations are not
permissible by law. In addition, alterations may result in
damage to the catalysts, increased fuel consumption and
impaired engine running conditions.
e. Irregular engine running conditions should be
corrected immediately at a qualified service station.
Such irregular running conditions can influence the
proper function of the emission control system.
"CHECK ENGINE" indicator lamp in the instrument
cluster: If the lamp comes on when the engine is running,
it indicates a malfunction of the engine management
system or emission control system.
We recommend that you have the malfunction checked as
soon as possible.
11