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Troubleshooting
28
2 Problem Possible cause/consequence Suggested solutions
D
The red coolant warning
lamp lights up while the
engine is running. You will
also hear a warning tone. The coolant temperature has
exceeded 130
†. The engine is
not being cooled sufficiently and
may be damaged .
The coolant level may be too low. X
Stop the vehicle as soon as possible. Pay attention to the traffic
conditions as you do so.
X Allow the engine and coolant to cool.
X Check the coolant level. Observe the warning note s
( Y page 209). Top up the coolant if necessary.
X Have the coolant system checked at a qualified specialist work-
shop if the coolant needs topping up more often than usual .
If the coolant level is correct, the radiator fan may be faulty. In this
case:
X Do not continue driving under any circumstances .
X Consult a qualified specialist workshop. ±
The yellow engine diagnos-
tic warning lamp lights up
while the engine is run-
ning. Vehicles with a diesel engine: the
fuel tank has run dry. X
Start the engine three to four times after refuelling.
Emergency running mode is cancelled. The vehicle need not be
checked. Practical advice
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B
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Troubleshooting
28
3 Problem Possible cause/consequence Suggested solutions
±
The yellow engine diagnos-
tic warning lamp lights up
while the engine is run-
ning. There may be a malfunction:
R
in the fuel injection system or
R in the exhaust system or
R in the ignition system (on vehi-
cles with a petrol engine)
The emission limit values may be
exceeded and the engine may be
running in emergency mode. X
Have the vehicle checked as soon as possible at a qualified spe -
cialist workshop. =
The red SRS warning lamp
lights up while the engine
is running. G
Risk of injury
The restraint systems are faulty .
The airbags or belt tensioners
may either be triggered uninten-
tionally or, in the event of an acci-
dent, not be triggered at all. X
Visit a qualified specialist workshop immediately. <
The red seat belt warning
lamp lights up for 6 sec-
onds after the engine
starts up. 16 The seat belt warning lamp
reminds the driver and front
passenger to fasten their seat
belts. X
Fasten your seat belt (Y page 98). 16
Only for certain countries Practical advice
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Troubleshooting
29
1 Problem Possible cause/consequence Suggested solutions
Vehicles with a petrol engine:
The engine is not running
smoothly and is misfiring. The engine electronics or
a
mechanical component of the
engine control unit have been
damaged. X
Only depress the accelerator pedal slightly.
X Have the cause rectified immediately at a qualified specialist work-
shop .
Otherwise, non-combusted fuel may get into the catalytic converter
and damage it. A coolant temperature of over
120 °C is displayed. The coolant
warning lamp may also be on and
a warning signal may sound
(
Y page 123). The coolant level is too low. The
coolant is too hot and the engin
e
is no longer being cooled suffi-
ciently. X
Stop as soon as possible and allow the engine and the coolant to
cool down.
X Check the coolant level (Y page 209). Observe the warning notes
as you do so and top up the coolant if necessary. If the coolant level is correct, the
radiator fan may be faulty. The
coolant is too hot and the engin
e
is no longer being cooled suffi-
ciently. X
If the coolant temperature is less than 120°C, you can continue
driving to the nearest qualified specialist workshop.
X Avoid heavy loads on the engine as you do so, e.g. when driving on
mountain roads and stop/start driving . Practical advice
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Troubleshooting
29
7 Problem Possible cause/consequence Suggested solutions
The engine cannot be started
using the key. The on-board voltage is too low. X
Switch off non-essential consumers, e.g. seat heating* or interio r
lighting, and try to start the engine again.
If this does not work :
X Check the starter battery and recharge it if necessary
(Y page 326).
or
X Jump-start the vehicle (Y page 328).
or
X Consult a qualified specialist workshop. The engine cannot be started
using the key. The steering lock is mechanically
blocked. X
Remove the key and reinsert it into the ignition lock. At the sam e
time, turn the steering wheel in both directions. Practical advice
* optional
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Towing and tow-startin
g 329
The positive and negative contacts are loca-
ted on the front bulkhead on the right-han d
side of the vehicle. 1
Positive terminal of donor batter y
2 Cove r
3 Positive contact on your vehicle
4 Negative contact on your vehicle
5 Negative terminal of donor battery
X Slide cap 2of positive contact 3in the
direction of the arrow.
X Attaching the jump-start cable to the donor
battery first, connect positive terminal 1
of the donor battery and positive contact
on your vehicle 3.
X Start the engine of the donor vehicle and
run it at idling speed . X
Attaching the jump-start cable to the donor
battery first, connect negative terminal 5
of the donor battery and negative contact
on your vehicle 4.
X Start the engine.
X Electrical consumers can be switched on
again. Do not switch the lights on however ,
as this will overload the battery.
X First disconnect the jump lead from nega -
tive terminals 4and 5, then from positiv e
terminals 1and 3.
X Have the battery checked at a qualified
specialist workshop, e.g. a Mercedes-Benz
Service Centre. Towing and tow-starting
Points to remember
G
Risk of accident
If you tow the vehicle, you must use a rigid
towing bar if:
R the engine is not running
R there is a brake system malfunctio n
R the voltage supply or the vehicle's elec-
trical system is damage d
There is no power assistance for the steer-
ing when the engine is not running.
It is better to have the vehicle transported
than to have it towed.
When towing, observe the legal requirement s
in all countries concerned.
! You may tow the vehicle for a maximum
of 50 km. A towing speed of 50 km/h must
not be exceeded.
With towing distances over 50 km, the
entire vehicle needs to be lifted up and
transported.
! Only secure the tow cable or towing bar
to the towing eyes. You may otherwise
damage the vehicle. Practical advice
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