Mercedes Benz Intelligent Servo Module(ISM)|What they Do and How it Works

December 12, 2019MechVibesblog

How often does your Mercedes Benz refuses to shift from park to drive, reverse or neutral? Stacked at a parking lodge as a result of a bad Intelligent Servo Module which makes it difficult to shift your vehicle’s gear.

For the past several years, car owners and car guys keep asking what is ISM and how does it work?

What are the causes of ISM related and its solutions.

In this article, we will discuss Mercedes-Benz Intelligent Servo Module(ISM) transmission problems.

This guide will help you narrow down Intelligent Servo Module, its transmission problems and teach you how to perform major repairs.

Mercedes-Benz builds very reliable transmissions and still in existence. 

These transmissions are mainly controlled with several electronic components and numerous sensors.

Intelligent Servo Modules are mainly built in new manufactured vehicles. Besides, they are mostly found in 7-speed transmissions.

Mercedes cars which are equip with these modules mainly have their gear selector leaver mounted on the vehicle’s steering column.



The Intelligent Servo Module(ISM) purposely built for DIRECT SELECT can be found and mounted on the transmission housing. 

This Mercedes Benz Intelligent Servo Module for DIRECT SELECT reads its signal from internal sensors such as the angle sensor which records actual position of range selector lever and shaft.

Besides, Intelligent Servo Module(ISM) receives connection from the Controller Area Network(CAN) which enables it share information with other units such as the;

  • Central Gateway Unit
  • Transmission Control Unit
  • Electronic Ignition Switch (EIS) control Unit
  • Steering Column Module
  • Instrument Cluster
  • Electronic Stability Program(ESP) control unit

Mercedes Intelligent Servo Module comes with huge cost in terms of replacement and a bit moderate in-terms of repairs.

Major causes of a faulty Intelligent Servo Module(ISM) is as a results of a blown fuse/relay, in-built component failures or crashed software code.

Moreover, Intelligent Servo Modules are purposely built for one specific car and installing a different or used ISM on a different vehicle requires programming and adaptation.

Besides, is advisable to try fixing it on the vehicle and see if it works, if not then you need to program it in order to match the vehicles Identification Number (VIN) information. 

The only way to get a used Intelligent Servo Module to work on your Mercedes-Benz is to find a third party that program ISM Modules.

This procedure may be referred to as flashing ISM(Intelligent Servo Module).

In other to know how a diagnose a faulty Intelligent Servo Module, is very important to focus on how the situation is related.


Mercedes Benz C250- Service Light Reset


  • Vehicle hardly start.
  • Vehicle’s gear won’t shift.
  • Revs at high rpm.
  • Cluster light goes off.
  • Vehicle won’t crank due to loss of communication from the Transmission Control Module.
  • Error data from actuator motor in the component A80 of the Intelligent Servo Module(ISM)
  • Car shakes badly in idle.

Further, since we have get to know major causes and symptoms regarding Intelligent Servo Module, is now time for us to dive deep on how to diagnose a faulty Intelligent Servo Module (ISM).


Mercedes-Benz- mechvibesblog

Mercedes Benz Intelligent Servo Module(ISM is found mainly on newly built 7-speed tronic transmissions with advance features.

A list are the names of Mercedes Benz vehicles built mainly with Intelligent Servo Module(ISM)

Mercedes A Class

Mercedes CLK

M-Benz CLC

Mercedes CL

Mercedes CLS

M-Benz E Class

Mercedes GLK

Super Mercedes Benz S-Class

Mercedes SL/SLK


Here, we will digest further on how to troubleshoot or diagnose a faulty Intelligent Servo Module.

Follow these step by step guide on other to diagnose a faulty Intelligent Servo Module(ISM) successfully.

Further, when diagnosing Mercedes Benz Intelligent Servo Module, you need a diagnostic scanner.

I recommend using advanced professional scanner that reads transmission codes.

In such related issues, using MB Star Diagnostic scanner would be of a great help.


Locate your OBD II port and connect diagnostic scanner. OBD port can be found straight downstream of the steering column or dashboard.

“Make sure to turn it on. Other scanners automatically turn on when is connect regarding ignition is on”


Select Vehicle(Mercedes Benz), model and year.


Select vehicle control Units. Make sure it reads all vehicle model details.


When done selecting vehicle model and year. Locate the Powertrain option and select.


Locate and select Intelligent Servo Module. If selected, you will be able to have a clear view of whats wrong with the vehicle at hand.

  • You will be able to read and clear vehicle’s fault codes.
  • Read vehicle’s live data
  • Perform accurate activation/adaptions



*1994 – Component A80 ( Direct Select defective/cannot reach specific target position)

*1984- Unknown fault code(Unknown fault type)

*5399- ESP CAN Signal gear selected from N15/3 is implausible

*C103- ETC No CAN message received from A80 ( Intelligent Servo Module for Direct Select)


Mercedes Benz Intelligent Servo Module(A80 component) is located on the outside of passenger side of the transmission and to remove is a major job.

It requires removal of drive shaft, transmission bracket and other additional loads. Loads. Getting a manual guide will be of a great help.


Its major job and I estimate labor and parts $2,300 


When repairing on stacked shifter in terms of module replacement, module needs to be “virgin” / new.

This shifter module needs to be program in order to match vehicles VIN or factory details.

Besides, when repairing a faulty Intelligent Servo Modules requires a specialized Mercedes Benz technician with advanced tools.

After repairs is complete on the ISM, its selection selector needs to be adapted with advanced diagnostic tools.


When working around Mercedes Benz Intelligent Server Module, its advisable to always go by the right procedure for a successful work done.

Besides, get a good or professional technician to help in working on these modules.

They are quite expensive, and much attention and accurate diagnostics is needed when doing stuff like this.

What’s your view, drop your comments!


Statements expressed above are only for informational purposes and should be independently verified.

Comments (9)

  • Alex Janpak

    September 21, 2020 at 8:43 am

    Where is the Aux Battery located ?

    1. David

      September 22, 2020 at 2:39 am

      Check underneath the steering Colum. Other models, it can be found at the trunk.

  • Enrique Caloca

    July 6, 2020 at 3:37 am

    Hi David, i find myself on the same issue. I have a S500 my question is if there is any difference on part number from Siemens and continental? so far what i have read is that continental might be more durable is that correct? also if is virgin or new what kind of programming is required?
    ex:A1644460710 (A 164 446 07 10)

    A0002704152 (A 000 270 41 52)

    A0002701652 (A 000 270 16 52)

    A0002701952 (A 000 270 19 52)

    A0002703252 (A 000 270 32 52)

    A0002704252 (A 000 270 42 52)

    A0002704452 (A 000 270 44 52)

    1. Chris

      July 13, 2020 at 3:51 am

      I worked on my 2006 ML350 today, managed to get all the wheel speed sensors done and took it for a drive, no issues and no sudden weird braking moments that scared the crap outta me months ago and I stopped driving it.
      All was well minus getting codes for low voltage due to the aux battery being dead.
      I had a new one but just hadn’t got around to changing it so I decided while i was at it I would do that too.
      I removed the main battery and then the dead aux battery and put the new one and replaced the main battery.
      Started up the car and ran my scanner again to make sure all those random low voltage codes were gone and sure enough they were, awesome however I noticed a new code, ISM.
      I thought WTF why is that coming up now?
      Scans showed DTC 1904, 1974, and 1978…read them and saw the car not in park.
      I thought huh, its running so I cleared and and thought I would go for another drive, well it will not go out of Park now and the dash is telling me not to change gears and drive to the shop LMAO…its in Park so I cannot go anywhere.
      How in the hell could the ISM get fried just changing the battery out!?
      I cannot understand how these engineers got their degrees devising such moronic failures from such simple tasks.

  • Merlin

    June 27, 2020 at 6:14 pm

    Thanks good info.

  • ibrahim ismair

    June 6, 2020 at 1:49 pm

    good explanation…. and helpful Thanx.

  • Thomas

    May 16, 2020 at 9:14 pm

    Can ISM cause my ml to go into emergency mode?

    1. David

      May 22, 2020 at 12:31 pm

      @ Thomas, It can prevent the vehicle from not starting and when you have a bad auxiliary battery.

  • Carol

    December 17, 2019 at 6:59 pm

    Aw, this was an incredibly good post. Finding the time and actual effort to make a really good article.

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