Emission Control; On-Board Diagnostic System (California Models Only) - Mercedes-Benz 420 SEL 1989 Owner's Manual

Emission Control

Certain systems of the engine serve
to keep the toxic components of the
exhaust gases within permissible
limits required by law.
These systems, of course, will func­
tion properly only when maintained
strictly according to factory specifica­
tions. Any adjustments on the engine
should, therefore, be carried out only
by qualified MERCEDES-BENZ tech­
nicians. The adjustments of the en­
gine should not be altered in any way.
Moreover, the specified service and
maintenance jobs must be carried out
regularly according to MERCEDES-
BENZ servicing requirements. For de­
tails refer to the Maintenance Booklet.
70
Warning!
Inhalation of exhaust gas is
hazardous to your health. All ex­
haust gas contains carbon
monoxide, and inhaling it can
cause unconsciousness and lead
to death.
Do not run the engine in confined
areas (such as a garage) which
are not properly ventilated. If you
think that exhaust gas fumes are
entering the vehicle while driving,
have the cause determined and
corrected immediately. If you
must drive under these condi­
tions, drive only with at least one
window fully open.
On-Board Diagnostic System
(California models only)
The CIS-E control unit monitors emis­
sion control components that either
provide input signals to or receive
output signals from the control unit.
Malfunctions resulting from interrup­
tions or failure of any of these compo­
nents are indicated by the "CHECK
ENGINE" indicator lamp in the instru­
ment cluster and are simultaneously
stored in the CIS-E control unit.
If the "CHECK ENGINE" indicator
lamp comes on, have the system
checked at your authorized
MERCEDES-BENZ dealer at the
first opportunity.
An on-board test connection with
pushbutton and light emitting diode
(LED) is located on the engine com­
partment firewall, allowing the accu­
rate detection of system malfunctions.