ECU MERCEDES-BENZ B-CLASS HATCHBACK 2015 Workshop Manual

Display messages
Possible causes/consequences and
M
MSolutions be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above. The wheels could therefore lock if you brake
hard, for example.
The steerability and braking characteristics may be severely affected.
The braking distance may increase in an emergency braking situation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. ÷
currently unavaila‐ currently unavaila‐
ble ble
See
SeeOwner's
Owner's Man‐
Man‐
ual
ual ESP
®
, BAS, the HOLD function, RBS, hill start assist and PRE‑SAFE ®
are temporarily unavailable.
The adaptive brake lights and COLLISION PREVENTION ASSIST PLUS
may also have failed.
In addition, the ÷,åandJ warning lamps may light up in
the instrument cluster.
ATTENTION ASSIST is deactivated.
The self-diagnosis function, for example, may not be complete.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above.
The braking distance may thus increase in an emergency braking sit-
uation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Carefully drive on a suitable stretch of road, making slight steering
movements at a speed above 20 km/h.
If the display message disappears, the functions mentioned above are available again.
If the multifunction display still shows the display message:
X Drive on carefully.
X Consult a qualified specialist workshop immediately. Display
messages
191On-board computer and displays Z

Display messages
Possible causes/consequences and
M
MSolutions ÷
inoperative inoperative
See
SeeOwn‐
Own‐
er's Manual
er's Manual ESP
®
, BAS, the HOLD function, RBS, hill start assist and PRE‑SAFE ®
are not available due to a malfunction.
The adaptive brake lights and COLLISION PREVENTION ASSIST PLUS
may also have failed.
In addition, the ÷,åandJ warning lamps may light up in
the instrument cluster.
ATTENTION ASSIST is deactivated.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above.
The braking distance may thus increase in an emergency braking sit-
uation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. T!
÷
inoperative inoperative See
SeeOwn‐
Own‐
er's Manual
er's Manual EBD (electronic brake force distribution), ABS, BAS, ESP
®
, the HOLD
function, RBS, hill start assist and PRE-SAFE ®
are not available due to
a malfunction.
The adaptive brake lights and COLLISION PREVENTION ASSIST PLUS
may also have failed.
A warning tone sounds.
The ÷, å,!andJ warning lamps may also light up in the
instrument cluster.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above. The front and rear wheels could therefore lock, for example, if you brake hard.
The steerability and braking characteristics may be severely affected.The braking distance may increase in an emergency braking situation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. 192
Display
messagesOn-board computer and displays

Drive system
Display messages
Possible causes/consequences and
M
MSolutions +
Top up coolant See Top up coolant See
Owner's Manual Owner's Manual The coolant level is too low.
! Avoid making long journeys with too little coolant in the cooling
system. The drive system will otherwise be damaged.
X If the coolant needs topping up more often than usual, have the
cooling system checked at a qualified specialist workshop. #
See Owner's Manual See Owner's Manual The 12 V battery is no longer being charged.
X Stop the vehicle immediately, paying attention to road and traffic
conditions, and switch off the drive system.
X Secure the vehicle against rolling away (Y page 145).
X Do not drive on.
X Do not tow the vehicle.
X Consult a qualified specialist workshop. #
Stop vehicle See Stop vehicle See
Owner's Manual Owner's Manual The 12 V battery is no longer being charged and the battery charge
level is too low.
A warning tone also sounds.
X Stop the vehicle immediately, paying attention to road and traffic
conditions, and switch off the drive system.
X Secure the vehicle against rolling away (Y page 145).
X Do not drive on.
X Do not tow the vehicle.
X Consult a qualified specialist workshop. High-voltage battery
Display messages
Possible causes/consequences and
M MSolutions Ý
Battery reserve Battery reserve
level level The charge level of the high-voltage battery has dropped into the
reserve range.
When the remaining range is 0 km, the message appears again. The
power available is then continuously reduced. The reduction in power
is represented in the E-CELL display (Y page 173).
X Charge the high-voltage battery. Û
Battery capacity Battery capacity
too too
low
lowStop
Stop Charge
Charge
immediately
immediately A warning tone also sounds. The E
‑CELL display (Ypage 173) and the
charge level display (Y page 174) go down to 0. The charge level of the
high-voltage battery is so low that operation is no longer possible. The drive system cannot be restarted.
If you then try to restart the drive system, the Battery capacity
Battery capacity
too low Stop Charge immediately too low Stop Charge immediately message appears.
X Park the vehicle and charge the high-voltage battery. 204
Display
messagesOn-board computer and displays

Safety
Seat belts Problem
Possible causes/consequences and
M
MSolutions ü
Only for certain coun-
tries: the red seat belt
warning lamp lights up
for 6 seconds after the
drive system starts.
The seat belt warning lamp reminds the driver and front passenger to
fasten their seat belts.
X Fasten your seat belt (Y page 37).ü
Only for certain coun-
tries: the red seat belt
warning lamp lights up
after the drive system
starts. In addition, a
warning tone sounds for
up to 6 seconds.
The driver's seat belt is not fastened.
X Fasten your seat belt (Y page 37).
The warning tone ceases. ü
The red seat belt warning
lamp lights up after the
drive system starts, as
soon as the driver's or
the front-passenger door is closed. The driver or passenger has not fastened their seat belt.
X Fasten your seat belt (Y page 37).
The warning lamp goes out. There are objects on the front-passenger seat.
X Remove the objects from the front-passenger seat and stow them in
a secure place.
The warning lamp goes out. ü
The red seat belt warning
lamp flashes and an
intermittent audible
warning sounds. The driver or passenger has not fastened their seat belt. At the same
time, you are driving faster than 25 km/h or have briefly driven faster
than 25 km/h.
X Fasten your seat belt (Y page 37).
The warning lamp goes out and the intermittent warning tone
ceases. There are objects on the front-passenger seat. At the same time, you
are driving faster than 25 km/h or have briefly driven faster than
25 km/h.
X Remove the objects from the front-passenger seat and stow them in
a secure place.
The warning lamp goes out and the intermittent warning tone
ceases. 214
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Safety systems
Problem
Possible causes/consequences and
M
MSolutions J
The yellow brake system
warning lamp is lit while
the drive system is run-
ning. The brake system is malfunctioning.
G WARNING
The braking characteristics may be affected.
There is a risk of an accident.
X Drive on taking extra care.
X Consult a qualified specialist workshop immediately. J
The yellow brake system
warning lamp is lit while
the drive system is run-
ning. RBS (Recuperative Brake System) is unavailable due to a malfunction.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
function listed above.
Braking efficiency may be impaired.
X Drive on taking extra care.
X Consult a qualified specialist workshop immediately. J
The red brake system
warning lamp is lit while
the drive system is run-
ning. A warning tone also
sounds. G
WARNING
The brake boosting effect is malfunctioning and the braking charac-
teristics may be affected.
There is a risk of an accident.
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions. Do not continue driving
under any circumstances.
X Safeguard the vehicle against rolling away (Y page 145).
X Consult a qualified specialist workshop.
X Observe the additional display messages in the multifunction dis-
play. Warning and indicator lamps in the instrument cluster
215On-board computer and displays Z

Problem
Possible causes/consequences and
M
MSolutions J
The red brake system
warning lamp is lit while
the drive system is run-
ning. A warning tone also
sounds. There is insufficient brake fluid in the brake fluid reservoir.
G WARNING
Braking efficiency may be impaired.
There is a risk of an accident.
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions. Do not continue driving
under any circumstances.
X Safeguard the vehicle against rolling away (Y page 145).
X Do not top up the brake fluid. Topping up will not rectify the fault.
X Consult a qualified specialist workshop.
X Observe the additional display messages in the multifunction dis-
play. !֌J
The yellow ABS, ESP
®
,
ESP ®
OFF and brakes
warning lamps are lit
while the drive system is running. ABS (Anti-lock Braking System) has been deactivated due to a fault.
Therefore, BAS (Brake Assist), COLLISION PREVENTION ASSIST
PLUS, ESP ®
(Electronic Stability Program), RBS, PRE ‑SAFE®
, the
HOLD function, hill start assist and the adaptive brake lights, for
example, are also deactivated.
ATTENTION ASSIST is deactivated.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above. The wheels could therefore lock if you brake
hard, for example.
The steerability and braking characteristics may be severely affected. The braking distance may increase in an emergency braking situation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Observe the additional display messages in the multifunction dis-
play.
X Drive on carefully.
X Consult a qualified specialist workshop immediately.
If the ABS control unit is malfunctioning, other systems may also not
be available, e.g. the navigation system. 216
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Problem
Possible causes/consequences and
M
MSolutions !֌J
The yellow ABS, ESP
®
,
ESP ®
OFF and brakes
warning lamps are lit
while the drive system is running. ABS is temporarily unavailable. Therefore, BAS, RBS, COLLISION PRE-
VENTION ASSIST PLUS, ESP ®
, EBD (electronic brake force distribu-
tion), PRE‑SAFE ®
, the HOLD function, hill start assist and the adaptive
brake lights, for example, are also deactivated.
Possible causes:
R Self-diagnosis is not yet complete
R The on-board voltage may be insufficient.
ATTENTION ASSIST is deactivated.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above. The front and rear wheels could therefore lock, for example, if you brake hard.
The steerability and braking characteristics may be severely affected.The braking distance may increase in an emergency braking situation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is a risk of an accident.
X Carefully drive on a suitable stretch of road making slight steering
movements at a speed above 20 km/h.
The functions mentioned above are available again when the warn-
ing lamp goes out.
If the warning lamp is still on: X Observe the additional display messages in the multifunction dis-
play.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. Warning and indicator lamps in the instrument cluster
217On-board computer and displays Z

Problem
Possible causes/consequences and
M
MSolutions !֌J
The yellow ABS, ESP
®
,
ESP ®
OFF and brakes
warning lamps are lit
while the drive system is running. EBD is faulty. Therefore, ABS, BAS, COLLISION PREVENTION ASSIST
PLUS, ESP ®
, RBS, PRE ‑SAFE®
, the HOLD function, hill start assist and
the adaptive brake lights, for example, are not available either.
ATTENTION ASSIST is deactivated.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above. The front and rear wheels could therefore lock, for example, if you brake hard.
The steerability and braking characteristics may be severely affected.The braking distance may increase in an emergency braking situation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Observe the additional display messages in the multifunction dis-
play.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. !֌J
The red brake system
warning lamp and the
yellow ABS, ESP
®
and
ESP ®
OFF warning lamps
are lit while the drive sys-
tem is running. ABS and ESP
®
are malfunctioning. Therefore, BAS, RBS, COLLISION
PREVENTION ASSIST PLUS, EBD, PRE ‑SAFE®
, the HOLD function, hill-
start assist and the adaptive brake lights, for example, are not avail-
able either.
ATTENTION ASSIST is deactivated.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above. The front and rear wheels could therefore lock, for example, if you brake hard.
The steerability and braking characteristics may be severely affected.The braking distance may increase in an emergency braking situation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Observe the additional display messages in the multifunction dis-
play.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. 218
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Problem
Possible causes/consequences and
M
MSolutions ֌J
The yellow ESP
®
, ESP ®
OFF and brakes warning
lamps are lit while the
drive system is running. ESP
®
, RBS, BAS, COLLISION PREVENTION ASSIST PLUS, PRE‑SAFE ®
,
the HOLD function, hill start assist and the adaptive brake lights are
not available due to a malfunction.
ATTENTION ASSIST is deactivated.
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above.
The braking distance may thus increase in an emergency braking sit-
uation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Observe the additional display messages in the multifunction dis-
play.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. 220
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Problem
Possible causes/consequences and
M
MSolutions ֌J
The yellow ESP
®
, ESP ®
OFF and brakes warning
lamps are lit while the
drive system is running. ESP
®
, BAS, PRE‑SAFE ®
, the HOLD function and hill start assist are
temporarily unavailable.
The adaptive brake lights and COLLISION PREVENTION ASSIST PLUS
may also have failed.
ATTENTION ASSIST is deactivated.
Self-diagnosis is not yet complete
G WARNING
The braking performance of the electric motor using recuperative
braking may be either reduced or not effective. If you do not make an
additional effort to apply the brake yourself, the braking effect may not be sufficient. If necessary, counteract the reduced regenerative brak-
ing effect by applying the brake yourself.
The brake system continues to function normally, but without the
functions listed above.
The braking distance may thus increase in an emergency braking sit-
uation.
If ESP ®
is not operational, ESP ®
is unable to stabilise the vehicle.
There is an increased danger of skidding and risk of an accident.
X Carefully drive on a suitable stretch of road, making slight steering
movements at a speed above 20 km/h.
The functions mentioned above are available again when the warn- ing lamp goes out.
If the warning lamp is still on: X Observe the additional display messages in the multifunction dis-
play.
X Drive on carefully.
X Consult a qualified specialist workshop immediately. Warning and indicator lamps in the instrument cluster
221On-board computer and displays Z