2008 MERCEDES-BENZ GL450 check engine light

439 Practical hints
What to do if …
ProblemPossible cause/consequenceSuggested solution
?(USA only)
±(Canada only)
The yellow engine malfunc-
tion indicator lamp comes
on while driving.There is a malfunction in:

The fuel management
system

The ignition system

The emission control system

Systems which affect
emissions
Such malfunctions may result in
excessive emissions values and
may switch the engine to its
limp-home (emergency opera-
tion) mode.
Have the vehicle checked as soon as
possible by an authorized
Mercedes-Benz Light Truck Center.
An on-board diagnostic connector is
used by the service station to link the
vehicle to the shop diagnostics system.
It allows the accurate identification of
system malfunctions through the read-
out of diagnostic trouble codes. It is lo-
cated in the front left area of the
footwell next to the parking brake pedal.
iSome states may by law require you to visit
a workshop as soon as the engine malfunction
indicator lamp comes on. Check local require-
ments.
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440 Practical hints
What to do if …
ProblemPossible cause/conse-
quenceSuggested solution
?(USA only)
±(Canada only)
The yellow engine malfunction
indicator lamp comes on while
driving.A loss of pressure has been
detected in the fuel system.
The fuel cap may not be closed
properly or the fuel system
may be leaky.Check the fuel cap (page 374).
If it is not closed properly:
Close the fuel cap.
If it is closed properly:
Have the fuel system checked by an
authorized Mercedes-Benz Light Truck
Center.
Vehicles with diesel engine:
Your fuel tank is empty.After refueling start, turn off and
restart the engine three or four times in
succession.
The limp-home mode is canceled. You do
not need to have your vehicle checked.
lThe red distance warning lamp comes on
while driving and you hear a warning sound.You are gaining too rapidly on
the vehicle ahead of you.Apply the brakes immediately.
Carefully observe the traffic situation.
You may need to brake or maneuver to
avoid hitting an obstacle.
The Distronic* has recognized
a stationary obstacle on your
probable line of travel.
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441 Practical hints
What to do if …
ProblemPossible cause/consequenceSuggested solution
vThe yellow ESP® warning lamp
comes on while the engine is
running.The ESP® has been switched off with the
ESP® switch or has switched off due to a
malfunction.
Risk of accident!
Adapt your speed and driving to the prevail-
ing road, weather, and traffic conditions.
Switch the ESP® back on (page 106).
Exceptions: (
page 105).
If the ESP
® cannot be switched back on:
Continue driving with added caution.
Observe additional messages in the
multifunction display that may appear.
Have the system checked at an autho-
rized Mercedes-Benz Light Truck
Center as soon as possible.
vThe yellow ESP® warning lamp
flashes while driving.The ESP® or the 4-ETS has come into
operation because of detected traction loss
of at least one tire.When driving off, apply as little throttle
as possible.
While driving, ease up on the accelera-
tor.
Adapt your speed and driving to the pre-
vailing road and weather conditions.
Do not deactivate the ESP®.
Exceptions: (
page 105).
Failure to follow these instructions
increases the risk of an accident.
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459 Practical hints
What to do if …
Display messagePossible cause/consequencePossible solution
PShift to P or N
to start engine.You have attempted to start the
engine with the KEYLESS-GO*
start/stop button while the auto-
matic transmission was set to
positionR orD.Set the automatic transmission to
positionP orN.
Make sure the brake pedal is depressed
when attempting to start the engine
with the KEYLESS-GO* start/stop but-
ton.
Only shift to P
when vehicle
is at a standstill.You have tried to shift the automat-
ic transmission into positionP us-
ing the gear selector lever although
the vehicle is still in motion.Stop the vehicle.
Apply the parking brake (page 67).
SRSRestraint Sys. Malfunction
Service RequiredThe system is malfunctioning.Drive with added caution to the nearest
authorized Mercedes-Benz Light Truck
Center.
Warning!G
In the event a malfunction of the SRS is indi-
cated as outlined above, the SRS may not be
operational. For your safety, we strongly
recommend that you contact an authorized
Mercedes-Benz Light Truck Center immedi-
ately to have the system checked; otherwise
the SRS may not be activated when needed
in an accident, which could result in serious
or fatal injury, or it might deploy unexpect-
edly and unnecessarily which could also re-
sult in injury.
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466 Practical hints
What to do if …
Symbol messages
Display symbolDisplay messagePossible cause/consequencePossible solution
ò Replace air filter.The air filter is clogged.Have the air filter checked by an
authorized Mercedes-Benz Light Truck
Center.
#The battery is no longer charging.
Possible causes:

alternator malfunctioning

broken poly-V-belt
Do not forget that the brake system
requires electrical energy and may be
operating with restricted capability.
Considerably greater brake pedal
force is required and the stopping dis-
tance is increased.
Stop the vehicle in a safe location or as
soon as it is safe to do so.
Apply the parking brake (page 67).
 Check the poly-V-belt.
If it is broken:
Do not continue to drive. Otherwise the
engine will overheat due to an inoperative
water pump which may result in damage
to the engine. Contact an authorized
Mercedes-Benz Light Truck Center.
If it is intact:
Drive immediately to the nearest
authorized Mercedes-Benz Light Truck
Center. Adjust driving to be consistent
with reduced braking responsiveness.
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469 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
;(USA only)
3(Canada only)
Check
Brake Fluid LevelThere is insufficient brake fluid
in the reservoir.Risk of accident! Stop the vehicle in a
safe location or as soon at is safe to do
so.
Apply the parking brake (page 67).
Contact an authorized Mercedes-Benz
Light Truck Center. Do not add brake
fluid! This will not solve the problem.
Warning!G
Driving with the message Check Brake
Fluid Level
displayed can result in an
accident. Have your brake system checked
immediately. Do not add brake fluid before
checking the brake system. Overfilling the
brake fluid reservoir can result in spilling
brake fluid on hot engine parts and the
brake fluid catching fire. You could be
seriously burned.
!If you find that the brake fluid in the brake
fluid reservoir has fallen to the minimum mark or
below, have the brake system checked for brake
pad thickness and leaks.
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470 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
Ï Coolant Level
Stop car, switch engine off.The coolant is too hot.
Among other possible causes
(the cooling fan could be
malfunctioning), the poly-V-belt
could be broken.Stop the vehicle in safe location or as
soon as it safe to do so.
Apply the parking brake (page 67).
Turn off the engine.
Check the poly-V-belt.
If it is broken:
Do not continue to drive. Otherwise, the
engine will overheat due to an inoperative
water pump which may result in damage
to the engine. Contact an authorized
Mercedes-Benz Light Truck Center.
If it is intact:
Do not continue to drive the vehicle with
this message displayed. Doing so could
result in serious engine damage that is
not covered by the Mercedes-Benz Limit-
ed Warranty.
(Continued on next page)
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472 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
B Top Up Coolant
See Operator’s ManualThe coolant level is too low.Add coolant (page 381).
If you have to add coolant frequently,
have the cooling system checked by an
authorized Mercedes-Benz Light Truck
Center.
Warning!G
Do not spill antifreeze on hot engine parts.
Antifreeze contains ethylene glycol which
may burn if it comes into contact with hot
engine parts. You could be seriously burned.
!Do not ignore the low engine coolant level
warning. Extended driving with the message and
symbol displayed may cause serious engine
damage not covered by the Mercedes-Benz
Limited Warranty.
Do not drive without sufficient amount of coolant
in the cooling system. The engine will overheat
causing major engine damage.
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