BMW SOS Emergency Call Malfunction: Diagnostics And Fixes

The “Emergency Call” malfunction message is triggered by a fault in the telematics system. An aged or faulty telematic backup battery is the most common fault in the Emergency Call system. In most cases, the battery will last for about three to five years, sometimes even less. In some cases, the water can leak through the shark fin’s seal into the control module. There were also a few faulty software releases throughout the production, but they are all fixed with the next update. However, since the SOS system operates as a part of a complex vehicle network, even the unplugged speaker or antenna cable will cause a system malfunction. 


  • A system fault will activate a warning message and it'll be noted in the control unit.
  • For diagnostic purposes, you'll need a scanner to review the error memory.
  • Usually, after changing the battery for example, you must remove error entries in order for the system to function properly again.


Emergency Call Malfunction Message Meaning

An "Emergency Call", or 'SOS Malfunction', means that the system isn't working. Various check-control messages might show on the instrument panel or iDrive display, depending on the generation of telematics in use.

Remember, the Emergency Call system is a complex web of diverse components and isn't solely reliant on the vehicle itself.

Essential external infrastructure is also needed for the system to function properly.

It's therefore critical to not just dive headfirst into a diagnostic procedure when you see a "Emergency Call" malfunction message in your BMW.

Understanding the broader context, including the evolution of BMW's telematics over the past quarter of a century, can offer you invaluable insights.

This knowledge can steer you towards resolving frequent problem areas such as outdated or defective telematic backup batteries that typically give up between three to five years.

Or issues like water leakage through the shark fin’s seal, occasional problematic software releases, and displaced speaker or antenna cables. It's important to note that resetting fault entries after replacing the battery is crucial to regain functionality.

Whereas, factors like mobile network faults might not necessarily display the malfunction message. Deducing these differences requires expertise. This comprehensive understanding can be your tool for troubleshooting, helping you tackle telematics unit issues and understand warnings with confidence.

How Emergency Call (SOS) System Works 

Although most of us recognize it as a nice illuminated button in the roof center console next to the sunroof switch, the BMW Emergency Call System is actually a quite complex ecosystem with the majority of its components located outside your BMW.

A manually activated emergency call. Source BMW AG.

BMW introduced an emergency call system back in 1997 as part of vehicle telematics called “mayday function” in E38, E39, and E46 models as an option. If a crash is detected, the vehicle will automatically initiate an emergency call, or you can manually call for help by pressing the SOS button.

Automatic Emergency Call information flow chart. Source: Rauscher, Stefan et al. “Enhanced Automatic Collision Notification (ACN) System – Improved Rescue Care Due to Injury Prediction – First Field Experience.” (2009).

When a car accident occurs, prompt notification and precise location are critical so that rescue personnel can arrive on the scene. It’s also useful to know the collision’s severity and the extent of injuries so that emergency personnel and specialty equipment can be assigned appropriately.

Once the automatic crash notification call is initiated, BMW telematics sends a notification that a crash has occurred, as well as the exact GPS coordinates and the vehicle identification number (VIN) to identify the model. Along with the data transfer, the car automatically calls the BMW Call Center, and the occupants can speak with specially trained operators.

Automatic emergency call initiated. Source: BMW AG

For the 2007 model year, BMW introduced an enhanced Automatic Crash Notification Technology (ACNT). These systems use onboard sensors to collect additional crash metrics that can be used to estimate crash severity. Additional data collected and transmitted include the crash delta in the longitudinal and lateral directions for each impact event, crash type, safety belt status for front seat occupants, airbag deployment status, the occurrence of multiple impact events, and rollover occurrence, among others. 

When the raw data is transmitted to the BMW call center, it is processed by an algorithm known as URGENCY, which estimates the risk of serious injuries based on crash conditions.

Based on crash parameters transmitted by the Emergency Call system, the algorithm calculates the risk of serious injury. Seriously injured occupants have one or more injuries with an Abbreviated Injury Severity (AIS) score of 3 or higher (this includes AIS 3, AIS 4, AIS 5, AIS 6, and fatally injured). MAIS3+ injured refers to people who require immediate medical attention due to potentially life-threatening injuries.

During the data transmission, the telematics control unit simultaneously establishes a voice communication channel between the occupants and BMW Call Center. The URGENCY algorithm works in the background and calculates the risk of serious injury. The BMW Call Center is then able to provide this information directly to the nearest 911 Public Safety Answering Point. A conference call with the vehicle is also possible if necessary.

The 911 (PSAP) system can then use these details to coordinate the appropriate rescues, such as dispatching a helicopter, an Emergency Doctor, or the Fire Department, as well as involving the EMS and the police.

Since its introduction, the Emergency Call (eCall) system has evolved, as have the vehicle components involved. But, just as any new invention invariably brings new problems, BMW telematic systems have done so throughout the generations.

The most notable issues are connected to the discontinuation of 2G technology back in 2017 and 3G in 2021. If the first case, the issue affected even the new unsold cars. Although the telematics service discontinuation will not trigger the eCall malfunction message, it really doesn’t make sense to repair the system that will not work. 

So, let’s have a look at all generations and the most common problems that come with each. 

Telematics Control Unit (TCU) 1997-2010

Unfortunately, most of the telematics systems in older BMW generations like the E46 3 Series, E39 5 Series, E53 X5, and E38 7 Series are inoperative today. Besides the fact that SIM contracts expired a long time ago, the telematics electronics installed in a trunk are mostly damaged by water and moisture. 

Most of my experience with these systems is connected to disabling them because of annoying check control messages “BMW Assist Inactive,” or “SOS Call System Failure.” 

Although the TCU system had a few notable enhancements during the production, we’ll skip them altogether as the system doesn’t work since about 2016-2017 because of phasing out the 2G cellular network. 

The solution to getting rid of the annoying check-control messages is to simply code the function out with NCS Expert and other capable coding apps. 

TCM_ALIVE_MONITOR -> nicht_aktiv
TCM_ID_MONITOR -> nicht_aktiv

The other go-around is to retrofit the NBT Evo iDrive system together with the ATM 4G telematics module. If the job is done right, the eCall system will operate even better than the original – only it will send the wrong VIN to BMW Call Center and a bit fewer data. 

Combox (CBX-ECALL)

From 03/2010 BMW started phasing out TCU and replacing them with Combox telematics. 

In cars equipped with telematics, the Combox houses two separate modules: CBX-MEDIA and CBX-ECALL. Combox without CBX-ECALL doesn’t have telematics capability (emergency call). 

Now, to determine does it even make sense to repair eCall you should know that COMBOX operates on 2G technology. As the 2G is already phased out a long time ago in most markets, the COMBOX telematics, including eCall, will not work. 

However, back in 2017 BMW had a technical campaign to solve this issue in the US. The owners of affected vehicles could choose to get a $300 voucher for BMW Accessories, a $200 Visa pre-paid credit card, or a hardware upgrade to 3G cellular technology. Now, if you chose money or vouchers, the telematics was completely deactivated for good. If, on the other hand, you chose to hardware upgrade, you had to pay $199 for a yearly service extension at the time. 

With the hardware upgrade, you got the COMBOX NG (Next Generation) installed and activated. The COMBOX NG can still work on some markets with 3G networks available, but not the US. 

The solution is to either disable the eCall function or retrofit 4G telematics. As far as I know, the official BMW “3G sunset” retrofit is available only for the F series. 

COMBOX_ID_MONITOR -> nicht_activ

TCB And ATM Telematics

The Telematics Communication Box (TCB) was introduced in 2013 and phased out the COMBOX. The notable improvement is the emergency backup battery installed directly in the TCB module. The battery is 4.8V with a capacity of 600 mAh. The backup battery serves as a power source for telematics if the voltage supply is interrupted. The battery can power the system for at least five minutes on its own. 

The battery’s service life is about five years and it’s the most common source of SOS Malfunction messages. At each start-up, the TCB is running a self-test which includes the battery test. When the battery state drops below a set threshold, you get a check control warning message. 

For this system, the most common fault is a dead backup battery. 

Diagnostics And Repair 

Before starting with any diagnostics you should first establish if your BMW’s telematics system is even capable to operate at your location. For the US this is simple → the telematics requires 4G technology, that is, all BMW models from 2017 with ATM. In most EU countries 3G will still work. In some markets, this service is not available at all. 

The telematics modules with backup batteries are installed either on the trunk floor or directly under the shark fin on the roof. The first one is a five-minute job, while the other one can take a few hours, depending on your skills. 

To replace the ATM backup battery in the roof you should remove the headliner completely. However, after I don’t know how many batteries I replaced, I’m able to change the battery in under 20 minutes on some models (not G20 or G30). This isn’t something you can do on the first try. 

Most Common Emergency Call System Problems

Aged or Faulty Backup Battery

Without exaggeration, this is the most common cause of eCall warning messages. The backup batteries are installed from TCB up to the latest ATM2 units. The service life of TCB batteries is about five years, and they often last even longer. Since the module is located on the trunk’s floor, replacing a battery is a five-minute job.

BMW TCB Ni-MH backup battery

Since the introduction of TCB2 the installation location is moved to the roof, directly under shark fin antenna. The battery for TCB2, ATM, and ATM2 is Lithium-Ion and should last longer then previously used nickel metal hydride (Ni-MH) battery. However, these Li-ION batteries can often fail after a few years because of the hardware fault. In fact, I have a box full of these failed batteries with good capacity in a hope I find some other use for them.

The problem when this battery dies is that you need to remove the complete headliner just to replace it, at least per BMW Service procedure. This is the reason why most BMW dealers will quote this job at $600 or more, even though the battery is only about $50. However, it can be done with only carefully lowering the rear part of the headliner. For sedan models you’ll need to remove the third brake light cover and C-pillar pannels. For X and Touring models you’ll have to remove at least C and D-pillar covers. In any case, it’s not simple since you’ll have to work blindly on most BMW models, like G02 X4 for example.

After you replace the battery you’ll have to clear the fault memory to get rid of the warning message.

Faulty Telematics Control Unit Due to Water Leak

This problem impacts BMW models equipped with telematics control units under the shark fin antenna on the roof, namely TCB2, ATM, and ATM2 control units. Water penetration under the shark fin's seal could affect the electronic module, causing inevitable corrosion.

In this case, the most common diagnostic trouble code (DTC) is B7F33C – Internal ECU Error or there’s no communication with the module at all.

As you can see in the example below, the sealant is missing leaving the way for the water to get in. The causes can be numerous, but they are mostly the result of resealing the shark fin cover because of some job or they can even be done at the factory. I’ve seen a lot of these fins taped with 3M double-sided tapes that will hold until the next pressure washer.

The BMW shark fin seal missing at one point. Source: BMW Technical Service 2016 SI B84 04 16.

Faulty or Not Connected Speaker or Microphone

Both the emergency speaker and microphone can trigger Emergency Call Malfunction message. Most of these faults occur after the job is done on the headliner (microphone) or with the driver’s footwell panel (speaker) and someone forgot to connect them again. However, both of these components can fail. In BMWs with a sunroof option, the clogged water drain can cause the water to enter the headliner and microphone. Luckily, the diagnostics for these faults are fairly easy as the diagnostic error code will guide to the faulty or not connected component.

Faulty Telematics Control Unit Due to Corrupted Software

This issue mostly affects roof-mounted TCB2 and ATM units. Track the issue to faulty software is also pretty easy. You need to read out your BMW’s ECUs (ECU Tree) with ISTA or E-Sys and look up for TCB/ATM module. I you’re using the E-Sys after you read the ECUs check for the software versions under the ECU:

BMW E-Sys screenshot showing ECUs with software file names under the ECU name.

Under the TCB2 or ATM module, you’ll find files named BTLD, HWEL, SWFL… and then some numbers. If one or more of these files contains only zeroes there’s a software problem in the control unit. Unfortunately, as far as I’m aware, you can’t fix this problem by reprogramming or updating the software. I’ve run into this issue a few times and each time I tried to update the software, but it never worked. The only solution was to replace the telematics module. However, since replacing a telematics module can be a real hassle, I would always try to flash it before proclaiming it dead.

With ISTA, just read out the ECUs and hover with the mouse pointer over the TCB box to open the window with software information.

BMW ISTA application screenshot showing the software file names for the ATM module. Source: BMW Technical Service 2016 SI B84 04 16.

The latest software issue is related to ATM2 telematics produced from May 2019 to September 2021. Due to missing parameters, the SIM card deosn’t connect to different cell networks. This problem can also cause other ConnectedDrive issues. The solution is a simple software update with i-Level 21-07-540 or higher.

Georg Meier

BMW technician since 1996. I began my automotive journey in 1993 as an apprentice mechanic at Automag, the world's oldest BMW dealership in Munich. With years of experience and dedication, I garnered a wealth of knowledge about the intricacies of BMW and MINI vehicles. The love/hate relationship with the brand led me to found BIMMERIST where I share expertise and insights with fellow enthusiasts.

Post navigation

    • Thank you for your feedback. I apologize for any inconvenience caused. I’ll add a section in the article on how to turn off the SOS system. You know you can disable the SOS feature by coding the option out?

  • Very informative. I’ve fitted a mmi module to my 2013 f30nbt I drive system to give me apple car play . Since this I’ve had the SOS system failure message. I’m Waiting on the replacement battery for the control unit. I Will check the microphone connections again as I worked on the microphone to install the MMi unit. I have replaced the cars main battery as I knew it was dying. And had disconnected it for the MMI install a new car battery made no difference, waiting on the module battery to see if it’s that

Leave a Reply

Your email address will not be published. Required fields are marked *