NHTSA ID Number: 11020873
Manufacturer Communication Number: LI54.21-P-079510
TSB/Document Date: 2025-07-24
Summary
Complaint Diverse functional limitations in the vehicle in combination with various warning and fault messages in the instrument cluster display. Cause Communication timeouts mean that communication errors may occur in the on-board electrical system, which can result in various fault messages being displayed in the instrument cluster. This could be down to delayed feedback from the drivetrain control unit (N127) (CPC) to other control units networked to the CAN bus. Information: • It may not be possible to attribute any communication errors stored in the control units on the CAN bus to a specific cause. • In rare instances, there may be a brief activation of the yellow warning lamp for engine diagnosis or there may be a sporadic delay with the start enable. • There may not be any specific fault codes present that indicate a specific component. Remedy Do not replace any components!!! 1. Connect charger (see AR54.10-P-1127WT). Note: An adequate voltage from the on-board electrical system battery must be guaranteed for the entire duration of the work procedure. Otherwise the control units could be damaged if an undervoltage occurs. Information: Observe the operating instructions of the charger. Information: Use the charger to ensure an adequate voltage (at least 12.5 V) from the on-board electrical system battery. 2. Connect diagnostic system (see AD00.00-P-2000-06FR). Note: Always use the latest XENTRY Diagnostics software release. Information: Strict compliance with the operation steps in XENTRY Diagnostics is absolutely essential. 3. Select control unit N127 (CPC) via the direct link using XENTRY Diagnosis. Information: To do so, select the following menu items: Control units view → Drive systems → N127 - "Powertrain" control unit (CPC). 4. Update software for control unit N127 (CPC) (see AR54.21-P-0014-01Y). Info: To do so, select the following menu items: Adaptations → Control unit update → Update control unit software. Information: You are then automatically guided through the steps "Update of control unit software" and "SCN coding". Always observe the following operation steps at all times. 5. Disconnect diagnostic device from vehicle (see AD00.00-P-2000-06FR). 6. Disconnect charger from vehicle (see AR54.10-P-1127WT).
Diverse functional limitations in the vehicle in combination with various warning and fault messages in the instrument cluster display
Topic number
LI54.21-P-079510
Version
1
Function group
54.21 - Control units / basic modules
Date
7/16/25
Validity
Model series 206, 214, 223, 236, 254 (all vehicles
with powertrain control unit (N127) (CPC) of control unit
variant
"CPC3")
Reason for change
null
Complaint
Diverse functional limitations in the vehicle in combination with various warning and fault messages in the instrument
cluster display.
Cause
Communication timeouts mean that communication errors may occur in the on-board electrical system, which can result in various fault messages being displayed in the instrument cluster.
This could be down to delayed feedback from the drivetrain control unit (N127) (CPC) to other control units networked
to the CAN bus.
Information:
•
•
•
It may not be possible to attribute any communication errors stored in the control units on the CAN bus to a specific cause
In rare instances, there may be a brief activation of the yellow warning lamp for engine diagnosis or there may
be a sporadic delay with the start enable.
There may not be any specific fault codes present that indicate a specific component.
Example image: Fault messages in instrument cluster:
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AG
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The reason for this could be down to delayed feedback from the control unit CPC3 to other control units networked on
the CAN bus.
Attachments
File
Description
1.jpg
Remedy
Do not replace any components!!!
*******************************************************************************************************
1.
Connect charger (see AR54.10-P-1127WT).
Note: An adequate voltage from the on-board electrical system battery must be guaranteed for the entire duration of the work procedure. Otherwise the control units could be damaged if an undervoltage occurs.
Information: Observe the operating instructions of the charger.
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Information: Use the charger to ensure an adequate voltage (at least 12.5 V) from the on-board electrical system
battery.
2.
-------------------------------------------------------------------------------------------------------------------------------Connect diagnostic system (see AD00.00-P-2000-06FR).
Note: Always use the latest XENTRY Diagnostics software release.
Information: Strict compliance with the operation steps in XENTRY Diagnostics is absolutely essential.
3.
-------------------------------------------------------------------------------------------------------------------------------Select control unit N127 (CPC) via the direct link using XENTRY Diagnosis.
Information: To do so, select the following menu items: Control units view → Drive systems → N127 - "Powertrain" control unit (CPC)
4.
-------------------------------------------------------------------------------------------------------------------------------Update software for control unit N127 (CPC) (see AR54.21-P-0014-01Y).
Info: To do so, select the following menu items: Adaptations → Control unit update → Update control unit software.
Information: You are then automatically guided through the steps "Update of control unit software" and "SCN coding". Always observe the following operation steps at all times
5.
-------------------------------------------------------------------------------------------------------------------------------Disconnect diagnostic device from vehicle (see AD00.00-P-2000-06FR).
6.
-------------------------------------------------------------------------------------------------------------------------------Disconnect charger from vehicle (see AR54.10-P-1127WT).
WIS-References
Document number
Title
Note
AR54.10-P-1127WT
Maintain on-board electrical system
Maintain on-board electrical system
voltage for testing and diagnosis work voltage for testing and diagnosis work
on the vehicle
on the vehicle
AD00.00-P-2000-06FR
Connect/disconnect diagnostic device
AR54.21-P-0014-01Y
Program control unit
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
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Overall vehicle > Power supply > Battery/On-board electrical system > Battery function > Damage
Communication/information > Assistance and warning systems > Parking assist > PARKTRONIC > Acoustic warning
malfunction > General
Overall vehicle > Safety and locking system > Drive authorization system DAS > Electronic ignition lock/steering lock
> Does not receive turn authorization
Overall vehicle > Safety and locking system > Drive authorization system DAS > Electronic ignition lock/steering lock
> Malfunction
Overall vehicle > Power supply > Battery/On-board electrical system > Battery/on-board electrical system indicator
lamp > Battery charge indicator/consumer shutoff > Illuminates white
Power generation > Engine management > Indicator lamp > Engine diagnosis > lit
Communication/information > Information display > Displays > Multifunction display > Function > Malfunction
Communication/information > Information display > Displays > Multifunction display > Multifunction display, error
messages > Implausible messages despite properly functioning message systems
Communication/information > Information display > Indicator lamp > Malfunction
Communication/information > Information display > Indicator lamp > lit
Overall vehicle > Networking > Diagnosis/software > Software update (add-on)
Overall vehicle > Networking > Diagnosis/software > Current problems
Overall vehicle > Power supply > Battery/On-board electrical system > Battery/on-board electrical system display
message > Battery/Alternator - Serviced Required
Overall vehicle > Networking > CAN/FlexRay communication > Malfunction
Overall vehicle > Networking > LIN communication > Malfunction
Overall vehicle > Networking > Gateway communication > Malfunction
Communication/information > Information display > Displays > Multifunction display > Multifunction display, error
messages > Drivetrain - Malfunction (white warning message)
Overall vehicle > Power supply > Fuel cell > Malfunction
Communication/information > Assistance and warning systems > Blind spot assist > Malfunction
Control unit/fault code
Control unit
Fault text
N127 - Control unit "Drivetrain" (PTCU) (CPC3AMG)
-
N127 - Control unit "Drivetrain" (PTCU) (CPC3)
-
Operation numbers/damage codes
Op. no.
Operation text
Time
Damage
code
541011
Perform quick test
H
5440Z
540991
Program and code CPC3 control unit
(after quick test)
H
5440Z
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Note
Page 4 / 4
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TSB/Document ID: LI54.21-P-079510
Replacement Service Bulletin Number:
MFR Communication Date: 2025-07-17
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: ELECTRICAL SYSTEM
MFR Component System:
MFR Component Subsystem:
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