Noise Concerns from Suspension - Active Body Control (Option Code 490)
Topic number

LI32.50-P-079670

Version

1

Function group

32.50 - Active Body Control (ABC)

Date

8/28/25

Validity

Model series 223 and 167 with SA code 490 (Active Body
Control).
Does NOT include AMG models.

Reason for change

Complaint
1. Noises in recovery mode with the vehicle stationary
2. Noises when driving in a straight line on rough terrain
3. Noises when cornering and performing alternate steering movements
4. Non-assignable noises

Attachments
File

Description

Bouncing Noise.mov

Concern 1 and 2. Normal operating noise of the high
pressure pumps in recovery mode and when driving in a
straight line on rough terrain.

High Pressure Pump Noise Direction Changes.mp4

3. Reversing noise of the high pressure pump when steering quickly in the opposite direction.

Cause
Concern 1 - Noises in recovery mode with the vehicle stationary
Concern 2 - Noises when driving in a straight line on rough terrain.
These are normal operating noises of the hydraulic high-pressure pumps.
Explanation:
This is the "preview noise" which is heard when recovery mode is in operation, but which can also occur when driving
over very uneven ground in the Comfort and Curve drive programs.
This is a normal operating noise which is caused by the hydraulic high-pressure pumps (MPE).
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To compensate for the unevenness of the ground, large oil flows need to be generated and to do so, the MPEs turn at
very high rotational speeds.
Note:
In the "ECO" drive program, the "Preview" function is deactivated so these noises should not occur when driving over
uneven terrain; however the vehicle body will move noticeably.
Concern 3 - Noises when cornering and performing alternate steering movements - reversing noise.
Repeated rapid steering out of a curve generates a "grunting" noise.
Explanation: This noise is caused by the MPEs when the pump's direction of rotation is reversed.
Note: The reversing noise can occur in all drive programs, but is most clearly reproducible in the Curve drive program
and in Curve level 3.
Carry out an evaluation firstly in Curve levels 1 to 3 (at the highest Curve level 3, the noise will also be at its loudest!),
and then in the Comfort drive program.
Concern 4 - Non-assignable noises.

Remedy
Generally check whether the same noises also occur in ECO mode - in this mode the Preview/ROAD SURFACE
SCAN function is deactivated and the high-pressure pumps run at reduced speed.
Consequently, it is possible to differentiate between normal operating noises and unusual noises.
Regarding 1, 2: Explain the high-pressure system, replacing the suspension struts or pumps is not useful, as these
noises are caused by the high-pressure pump unit and should be regarded as normal operating noises.
Regarding 3: This is currently a normal operating noise and represents the series production configuration; consequently replacing the components is not useful.
Regarding 4: There will certainly be other unknown noises that we are not yet familiar with; therefore please report
these as well. For these, create a TIPS case and include informative video recordings of the noises.
The driving situation in the drive program in which the noises occur should be shown.
For comparison, also attach a recording of this same driving situation in ECO mode.
Additional attachments required:
- Logs for control units N51/8, M67, M67/1, M67/2, M67/3.
- Actual values for the pressures of the four hydraulic high-pressure pumps at standstill.

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
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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
Chassis/suspension > Suspension/Dampening > Suspension system noises > whistles/hisses
Chassis/suspension > Suspension/Dampening > Suspension system noises > Thumping
Chassis/suspension > Suspension/Dampening > Suspension system noises > Metallic noise
Chassis/suspension > Suspension/Dampening > Active body control > Noises > Grunting
Chassis/suspension > Suspension/Dampening > Active body control > Noises > Thumping/rumbling
Chassis/suspension > Suspension/Dampening > Active body control > Noises > Whistling/hissing/flowing
Chassis/suspension > Suspension/Dampening > Active body control > Noises > Tandem pump

Operation numbers/damage codes
Op. no.

Operation text

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Time

CCUSHWA

Damage
code

Note

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