Yellow warning message for 12V battery in IC, fault code B1FCB97
Topic number

LI54.10-P-073164

Version

3

Function group

54.10 - Battery, power supply, voltage converter

Date

3/4/26

Validity

All

Reason for change

Information was removed

Complaint
Yellow information message in driver display (instrument cluster): "Switch on motor to charge the 12V battery"

Attachments
File

Description

12V_Meldung_223.jpg

IC Message

Cause
The state of charge (SOC) of the 12V battery has dropped to 45% or less.

Attachments
File

Description

Beispiel_lange_unverriegelte_Parkzeit_und_Nutzung_Headunit.png

Example: Discharge due to vehicle being parked and unlocked and use of head unit (see network activity time)

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Beispiel_Entladung_bei_Werkstattarbeiten_ungenügendes_Stützen.png

Example: Discharge during workshop operations - no
charger to support on-board electrical system

Beispiel_lange_unverriegelte_Parkzeit.png

Example: Discharge due to vehicle being parked and unlocked and use of head unit (see network activity time)

Beispiel_Entladung_durch_Klemme15_im_Stand.png

Example: Discharge due to active terminal 15 while stationary

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Example_discharge_due_to_activity_on_terminal15.png

Example: Discharge due to active terminal 15 while parked

Example_discharge_during_works_at_vehicle_due_to_no_support_of_battery.png

Example: Discharge due to no support of battery during
workshop time

Example_parking_times_with_open_vehicle_and_Headu- Example: Discharge due to long parking times with open
nit_use.png
vehicle and use of head unit (network activity time)

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Example_parking_times_with_open_vehicle.png

Example: Discharge due to long parking times with open
vehicle and use of head unit (network activity time)

Remedy
This warning message appears as soon as the state of charge (SOC) of the 12V primary battery drops below 45%.
This message is displayed to safeguard the vehicle's starting ability.
At the same time as the display appears in the instrument cluster, customers with a linked Mercedes me connect account also receive a push notification via the app/by email (if this function is activated).
The battery must be charged to a state of charge (SOC) of at least 50%. To do this, an external charger can be connected (please comply with AR54.10-P-1133S) or the vehicle can be driven (by the customer) for 30 to 60 minutes.
Please make customers aware of how the vehicle behaves:
•
•
•

If the vehicle is used for short journeys, the battery state of charge may slowly drop to less than 45% – a negative charge balance
A negative charge balance will also occur if the vehicle is used while stationary without running the engine, e.g.
if the head unit is used, the ignition is switched on, or other comfort & convenience power consumers, e.g. seat
heating/seat ventilation, are active.
An unlocked vehicle may increase consumption, because certain vehicle functions are actively kept ready for the
customer. In combination with Keyless-Go or flush-mounted door handles, the vehicle may be woken up if the
vehicle key is detected in the vicinity of the vehicle.

The cause of the discharge can be identified with the aid of the onboard electrical system data in the EZS using XENTRY Diagnosis. See attached examples for identifying typical customer situations (e.g. operation with ignition on, operation of head unit while stationary or vehicle unlocked while parked).
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Vehicles with code B01+801: When charging while stationary, the 48V battery must have a state of charge (SOC) of
70% before the 12V primary battery, or the secondary battery in the case of code 503, can be charged.
To ensure optimum battery care, please also comply with the existing Service Information documents regarding the
handling of stock vehicles (SI54.10-P-0024A) and on remaining in transport mode (SI54.00-P-0004A) until immediately before handover to end customers.
Special note: Do not replace any parts, if the message has occurred due to battery discharge as a result of the driving
profile or the ignition being switched on (see attached examples); in such cases separate warranty and goodwill invoicing is not possible, as this is a normal on-board electrical system protection function. Likewise battery care and recharging do not qualify as a W&G case. Please advise customers accordingly regarding the above-mentioned issues relating to vehicle use.

Disclaimer
NOTE: The information contained in this document is intended for use by trained, professional technicians with the
knowledge to properly and safely perform diagnosis and repairs on Mercedes-Benz vehicles, using Mercedes-Benz
approved tools and equipment. It informs service technicians about conditions that could occur in certain vehicles and
provides information that could assist in proper vehicle diagnosis, service, or repair. It does not indicate that a defect
is present in any vehicle referenced in this document nor does it imply warranty coverage. DO NOT assume that a
symptom or condition, or a described cause of a symptom or condition, affects any particular vehicle or groups of vehicles, or that a described repair applies to any particular vehicle or groups of vehicles. There can be multiple causes
resulting in the same or similar symptoms or conditions described in this document, and trained professional service
technicians must use their diagnostic skills to make evaluations on a case-by-case basis. The information contained
in this document does not guarantee warranty coverage nor does it extend the vehicle’s warranty in any way.

Symptoms
Overall vehicle > Power supply > Battery/On-board electrical system > Battery/on-board electrical system display
message > Low voltage Switch off consumers
Overall vehicle > Power supply > Battery/On-board electrical system > Battery/on-board electrical system display
message > Low voltage Charge battery
Overall vehicle > Power supply > Battery/On-board electrical system > Battery/on-board electrical system display
message > Charging

Control unit/fault code
Control unit

Fault text

N73/3 - Electronic ignition lock (EZS) (EZS223)

B1FCB97 - The starter battery has a malfunction. The
system function is restricted.

Operation numbers/damage codes
Op. no.

Operation text

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Time

SAHARRY

Damage
code

Note

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