warning light MERCEDES-BENZ SLC 2019 Repair Manual

If the indicator/warning lamps do not light upat low temperatures, it is very likely that thedischarged battery has frozen. In this case,you may neither charge the battery nor jump-start the vehicle. The service life of a thawed-out battery may be shorter. The starting char-acteristics can be impaired, particularly at lowtemperatures. Have the thawed-out batterychecked at a qualified specialist workshop.
Read the battery charger's operating instruc-tions before charging the battery.
XOpen the hood.
XConnect the battery charger to the positiveterminal and ground point in the same orderas when connecting the donor battery in thejump-starting procedure (Ypage 260).
Replacing the 12 V battery
Observe the notes on the 12 V battery(Ypage 257).
Mercedes-Benz recommends that you havethe 12 V battery replaced at a qualified spe-cialist workshop, e.g. at an authorizedMercedes-Benz Center.
If you want to replace the battery yourself,observe the following notes:
RAlways replace a defective battery with abattery which meets the specific require-ments of the vehicle.
The vehicle is equipped with an AGM(Absorbent Glass Mat) technology battery.Full vehicle functionality is only guaranteedwith an AGM battery. For safety reasons,Mercedes-Benz recommends that you onlyuse batteries which have been tested andapproved for your vehicle by Mercedes-Benz.
RUse detachable parts such as breatherhoses, angled connecting pieces or terminalcovers from the battery which is to bereplaced.
RMake sure that the vent hose is always con-nected to the original opening on the bat-tery side.
RInstall existing or supplied cell caps to pre-vent gases or battery acid from escaping.
RMake sure that the detachable parts areconnected again in the same way.
Jump-starting
For the jump-starting procedure, use only the jump-starting connection point in the engine com-partment, consisting of a positive terminal and a ground point.
GWARNING
Battery acid is caustic. There is a risk of injury.
Avoid contact with skin, eyes or clothing. Do not inhale any battery gases. Do not lean over the
battery. Keep children away from batteries. Wash away battery acid immediately with plenty of
clean water and seek medical attention.
GWARNING
During charging and jump-starting, explosive gases can escape from the battery. There is a
risk of an explosion.
Particularly avoid fire, open flames, creating sparks and smoking. Ensure there is sufficient
ventilation while charging and jump-starting. Do not lean over a battery.
GWARNING
During the charging process, a battery produces hydrogen gas. If a short circuit occurs or
sparks are created, the hydrogen gas can ignite. There is a risk of an explosion.
260Jump-starting
Breakdown assistance

RMake sure that the positive terminal of a connected battery does not come into contact with
vehicle parts.
RNever place metal objects or tools on a battery.
RIt is important that you observe the described order of the battery terminals when connect-
ing and disconnecting a battery.
RWhen jump-starting, make sure that the battery poles with identical polarity are connected.
RIt is particularly important to observe the described order when connecting and disconnect-
ing the jumper cables.
RNever connect or disconnect the battery terminals while the engine is running.
GWARNING
A discharged battery can freeze at temperatures below freezing point. When jump-starting the
vehicle or charging the battery, gases can escape from the battery. There is a risk of an explo-
sion.
Allow the frozen battery to thaw out before charging it or jump-starting.
!Avoid repeated and lengthy starting attempts. Otherwise, the catalytic converter could bedamaged by the non-combusted fuel.
If the indicator/warning lamps do not light up at low temperatures, it is very likely that the dis-charged battery has frozen. In this case, you may neither charge the battery nor jump-start thevehicle. The service life of a thawed-out battery may be shorter. The starting characteristics canbe impaired, particularly at low temperatures. Have the thawed-out battery checked at a quali-fied specialist workshop.
Do not start the vehicle using a rapid charging device. If your vehicle's battery is discharged, theengine can be jump-started from another vehicle or from a donor battery using jumper cables.Observe the following points:
RThe battery is not accessible in all vehicles. If the other vehicle's battery is not accessible,jump-start the vehicle using a donor battery or a jump-starting device.
RYou may only jump-start the vehicle when the engine and exhaust system are cold.
RDo not start the engine if the battery is frozen. Let the battery thaw first.
ROnly jump-start from batteries with a 12 V voltage rating.
ROnly use jumper cables which have a sufficient cross-section and insulated terminal clamps.
RIf the battery is fully discharged, leave the battery that is being used to jump-start connectedfor a few minutes before attempting to start. This charges the battery slightly.
RMake sure that the two vehicles do not touch.
Make sure that:
RThe jumper cables are not damaged.
RBare parts of the terminal clamp do not come into contact with other metal parts while thejumper cables are connected to the battery.
RThe jumper cables cannot come into contact with parts which can move when the engine isrunning, such as the V-belt pulley or the fan.
XSecure the vehicle by applying the electric parking brake.
XShift the transmission to position].
XMake sure that the ignition is switched off. All indicator lamps in the instrument cluster mustbe off. When using the SmartKey, turn the SmartKey to position

Important notes on tire pressure
GWARNING
If the tire pressure drops repeatedly, the
wheel, valve or tire may be damaged. Tire
pressure that is too low may result in a tire
blow-out. There is a risk of an accident.
RCheck the tire for foreign objects.
RCheck whether the wheel is losing air or
the valve is leaking.
If you are unable to rectify the damage, con-
tact a qualified specialist workshop.
GWARNING
If you fit unsuitable accessories onto tire
valves, the tire valves may be overloaded
and malfunction, which can cause tire pres-
sure loss. Due to their design, retrofitted tire
pressure monitors keep the tire valve open.
This can also result in tire pressure loss.
There is a risk of an accident.
Only screw the standard valve cap or other
valve caps approved by Mercedes-Benz for
your vehicle onto the tire valve.
Use a suitable pressure gauge to check thetire pressure. The outer appearance of a tiredoes not permit any reliable conclusion aboutthe tire pressure. On vehicles equipped withthe electronic tire pressure monitor, the tirepressure can be checked in the on-board com-puter.
The tire temperature and pressure increasewhen the vehicle is in motion. This is depend-ent on the driving speed and the load.
Therefore, you should only correct tire pres-sures when the tires are cold.
The tires are cold:
Rif the vehicle has been parked with the tiresout of direct sunlight for at least three hoursand
Rif the vehicle has not been driven furtherthan 1 mile (1.6 km)
The tire temperature changes depending onthe outside temperature, the vehicle speedand the tire load. If the tire temperaturechanges by 18 ‡ (10 †), the tire pressurechanges by approximately 10 kPa (0.1 bar/1.5 psi). Take this into account when checking
the pressure of warm tires. Only correct thetire pressure if it is too low for the currentoperating conditions. If you check the tirepressure when the tires are warm, the result-ing value will be higher than if the tires werecold. This is normal. Do not reduce the tirepressure to the value specified for cold tires.The tire pressure would otherwise be too low.
Observe the recommended tire pressures forcold tires:
Ron the Tire and Loading Information placardon the B-pillar on the driver's side
Rin the tire pressure table on the inside of thefuel filler flap
Rprinted in yellow on the rim of the emer-gency/collapsible spare wheel (dependingon vehicle equipment)
Underinflated or overinflated tires
Underinflated tires
GWARNING
Tires with pressure that is too low can over-
heat and burst as a consequence. In addi-
tion, they also suffer from excessive and/or
irregular wear, which can severely impair the
braking properties and the driving character-
istics. There is a risk of an accident.
Avoid tire pressures that are too low in all
the tires, including the spare wheel.
Underinflated tires may:
Roverheat, leading to tire defects
Radversely affect handling
Rwear excessively and/or unevenly
Rhave an adverse effect on fuel consumption
Overinflated tires
GWARNING
Tires with excessively high pressure can
burst because they are damaged more eas-
ily by road debris, potholes etc. In addition,
they also suffer from irregular wear, which
can severely impair the braking properties
and the driving characteristics. There is a
risk of an accident.
272Tire pressure
Wheels and ti res

vehicle to a halt by braking carefully. Avoidabrupt steering movements.
The tire pressure monitor has a yellow warninglamp in the instrument cluster for indicatingpressure loss or a malfunction. Whether thewarning lamp flashes or lights up indicateswhether a tire pressure is too low or the tirepressure monitor is malfunctioning:
Rif the warning lamp is lit continuously, thetire pressure on one or more tires is signifi-cantly too low. The tire pressure monitor isnot malfunctioning.
Rif the warning lamp flashes for approx-imately a minute and then remains lit con-stantly, the tire pressure monitor is malfunc-tioning.
In addition to the warning lamp, a messageappears in the multifunction display. Observethe information on display messages(Ypage 201).
It may take up to ten minutes for a malfunc-tion of the tire pressure monitor to be indica-ted. A malfunction will be indicated by the tirepressure warning lamp flashing for approx-imately one minute and then remaining lit.When the malfunction has been rectified, thetire pressure warning lamp goes out after afew minutes of driving.
The tire pressure values indicated by the on-board computer may differ from those meas-ured at a gas station with a pressure gage. Thetire pressures shown by the on-board com-puter refer to those measured at sea level. Athigh altitudes, the tire pressure values indica-ted by a pressure gage are higher than thoseshown by the on-board computer. In this case,do not reduce the tire pressures.
The operation of the tire pressure monitor canbe affected by interference from radio trans-mitting equipment (e.g. radio headphones,two-way radios) that may be being operated inor near the vehicle.
Checking the tire pressure electroni-
cally
XMake sure that the SmartKey is in positionH(Ypage 118) in the ignition lock.
XPress theYorebutton on the steer-ing wheel to select theServ.Serv.menu.
XPress thecordbutton to selectTire PressureTire Pressure.
XPressv.The current tire pressure of each tire isshown in the multifunction display.
If the vehicle has been parked for over20 minutes, theTire pressure will beTire pressure will bedisplayed after driving a few minutesdisplayed after driving a few minutesmessage appears.
After a teach-in process, the tire pressuremonitor automatically detects new wheels ornew sensors. As long as a clear allocation ofthe tire pressure value to the individual wheelsis not possible, theTire Pressure MonitorTire Pressure MonitorActiveActivedisplay message is shown instead ofthe tire pressure display. The tire pressuresare already being monitored.
If an emergency spare wheel is mounted, thesystem may continue to show the tire pressureof the wheel that has been removed for a fewminutes. Be aware that the value displayed forthe position where the emergency spare wheelis fitted is not the same as the current tirepressure of the emergency spare wheel.
Tire pressure monitor warning mes-
sages
The tire pressure monitor detects a pressureloss in one or more tires:
RIf the tire pressure monitor detects a pres-sure loss in one or more tires, a warningmessage is shown in the multifunction dis-play. The yellow tire pressure warning lampthen lights up.
RIf thePlease Correct Tire PressurePlease Correct Tire Pressuremessage appears in the multifunction dis-play, the tire pressure in at least one tire istoo low. The tire pressure must be correctedwhen the opportunity arises.
RIf theCheck TiresCheck Tiresmessage appears in themultifunction display, the tire pressure in atleast one tire has dropped significantly. Thetires must be checked.
RIf theWarning Tire MalfunctionWarning Tire Malfunctionmes-sage appears in the multifunction display,the tire pressure in at least one tire hasdropped suddenly. The tires must bechecked.
Observe the instructions and safety notes inthe display messages in the "Tires" section(Ypage 201).
276Tire pressure
Wheels and tires