The most common causes of charging problems are a torn crankshaft pulley and alternator failure. The drive belt stops turning the alternator when the rubber insulator inside the pulley breaks. Alternator failures are uncommon and usually occur on older or high-mileage BMWs. In hybrid models, the most common problems are related to the DC-DC converter.
KEY FACTS
- A CHARGING MALFUNCTION MESSAGE APPEARS WHEN THE MAIN BATTERY VOLTAGE DROPS TOO LOW
- THE CRANKSHAFT PULLY’S CONDITION IS OFTEN OVERLOOKED DURING ROUTINE MAINTENANCE
- CONTRARY TO POPULAR BELIEF, A WEAK BATTERY WILL NOT CAUSE A CHARGING MALFUNCTION WARNING
- A FAULT IN THE INTELLIGENT BATTERY SENSOR (IBS) SYSTEM CAN CAUSE CHARGING PROBLEMS, BUT NOT CHARGING MALFUNCTION FAULT MESSAGE
- ON OLDER E-SERIES MODELS MOST COMMON CHARGING PROBLEMS ARE RELATED TO CORRODED BATTERY CABLE CONNECTIONS AT B+ TERMINALS
What to Do When Charging Malfunction Warning Appears
The faults like these will never happen when your BMW is parked at home. Theoretically, they could, but they won’t. Instead, they always happen when you need your BMW mostly.
Preferably, when you are in the middle of nowhere or crawling through manic urban traffic.
When the charging malfunction in iDrive or a red battery light in the instrument cluster appears, the complete vehicle electrical system is supported only by the battery. That is, the power steering, fuel pump, injectors, Valvetronic servo motor, transmission mechatronics, water pumps, air conditioning, audio system, headlights, and other 30+ control units will rely solely on the voltage left in the battery.
That means you have very little time till the engine shuts off, usually only a few minutes. The only thing you need to think about when the message appears is how and where to stop your BMW safely.
However, if you are risk taker type of person, you can try to prolong the inevitable by switching off all possible electrical consumers, but as the voltage drops your BMW will do it for you. The Intelligent Battery Sensor will report the state of the battery’s charge so that other modules can switch off consumers.
In most cases, the first thing you’ll notice is that the electrical power steering (EPS) has been turned off, implying that you’ll have to exert more steering effort. If the problem is a ripped crank pulley or alternator drive belt, this will also happen with hydraulic steering on older BMWs.
Here’s an example in which consumers are switched off after the battery state of charge drops below a specific limit. The table below is just for reference and it is different from model to model.
| Battery Energy Availability | Electrical Consumer | Measure |
| 78% | Heated rear window | Cycles (30 s on, 60 s off) |
| 76% | Seat heating, front, and rear | From stage 3 to stage 2 |
| 74% | Armrest heating | From stage 3 to stage 2 |
| 72% | Front seat heating | From stage 2 to stage 1 |
| 70% | Armrest heating | From stage 2 to stage 1 |
| 68% | Rear seat heating | Power consumption at 50% |
| 66% | Armrest heating, rear | From stage 2 to stage 1 |
| 52% | Mirror heating | off |
| 52% | Washer jet heating | off |
| 48% | Steering wheel heating | off |
| 40% | Seat heating | off |
| 38% | Electric auxiliary heater | off |
And so on till the 20% left. The most important thing I want to emphasize is that this drop happens rapidly after the alternator stops producing current. Once you start the engine, the BMW battery’s main task is to work as an electrical load balancer, not as a power source. So, instead of trying to manically turn off every possible consumer, you should focus on where to stop safely and call for help.
If you own a hybrid BMW, such as an X5 45e or 530e, and believe there is enough juice in the high-voltage batteries to keep driving, I must disappoint you. The 12V battery powers all ECUs that manages the high-voltage system, and the charging malfunction warning message means the 12V battery is no longer charged.
Quick Troubleshooting of Charging Malfunction
The first thing you want to check is if the alternator pulley is turning with the engine running. If the drive belt is not turning with the engine, the crankshaft pulley rubber is probably torn apart. The drive belt assemblies on modern BMWs are as reliable as it gets, so in most cases with at least a reasonably maintained BMW this should not be a problem.
However, when stranded on the road it might be difficult to even see the alternator and drive belt. This, of course, depends on the BMW model.
Basically, the older and simpler the car, they will be easier. On most current BMW models the drive belt is hidden behind the insulation and it’s hard to check without disassembling it.
In the picture above you can see the engine bay of the F82 M4 that I took for this post where you can at least have a look at the alternator and the drive belt.
With the E92 M3, it’s not that easy…
With that out of the way, we can move to the next step and check the system voltage. With a charged battery, start the engine and measure the voltage with a multimeter at the engine bay jump start points.
Depending on the battery state of charge, the voltage should be between 14V and 15V. If the readings are below or above these values, the next step is to rule out the IBS system fault.
For this, just unplug the IBS sensor at the negative battery lead and repeat the measurements. Without the IBS, the voltage supply system will go into a “limp mode” and operate as it does on normal cars without intelligent battery management.
Without IBS connected you should see readings in the range of about 14V to 14.5V.
With that out of the way, you need to rule out battery and ground cables.
OK, now you know the cause is the faulty alternator.
Most Common Charging Malfunction Problems
The alternator is Not Working Due to Torn Crankshaft Pulley
The crankshaft pulley, also known as a harmonic balancer, or in the ETK parts catalog as a vibration damper, is not like any other pulley. They are much more than a simple pieces of metal.
The crankshaft pulley drives the drive belt by distributing the rotational force of the crankshaft to the engine accessories via the driving belt. To dampen engine vibrations, BMW crankshaft pulleys have a rubber insulator ring between the internal and external parts of the pulley to prevent transmission of the engine vibration the drive belt and accessories like the alternator, power steering pump, water pump, AC compressor, etc…
When the rubber isolator breaks, the inner hub connected to the crankshaft will separate from the outer part connected to the drive belt. Depending on many factors, the center hub can partly or completely separate from the outer part. As the drive belt stops turning, the accessories powered by the belt will stop working. The most notable is the alternator which will trigger the charging malfunction warning message or red battery light.
Broken crankshaft pulleys can cause erratic engine run, engine vibrations, and grinding noise from the engine compartments in some cases, particularly with B46, B48, and B58 engines. It’s also possible that you’ll smell the burnt rubber, especially with Diesel engines like M57, N47, and N57, although you probably won’t notice any vibrations.
Depending on the model series, the following check control messages can appear:
- Charging malfunction
- Vehicle battery is not being charged!
- Engine too hot! Drive gently
- Engine overheated! Stop carefully
- Stop, exercising due care. Voltage supply.
- It is possible to continue driving. Engine temperature.
- Stop, exercising due care. Engine overheated!
After you read out the fault memory with a scanner, you’ll get DTC 210601 – Alternator, mechanical: Malfunction, or 2A1100 – Alternator: mechanical fault.
The solution is to replace the crankshaft pulley and check all belt-driven components for damage. To check the alternator, spin the alternator’s pulley by hand with the belt removed. If the alternator rotates freely without grinding noise and resistance, the alternator mechanical parts are OK. Also, check the axial and radial play of the alternator’s shaft – there should be no play.
The vibration damper rubber insulator located between the drive belt pulley and its center hub has either party or fully separated (torn). The separation will allow the two components to move independently from each other.
A crankshaft pulley is a mechanical device that is directly connected to the crankshaft of an engine. Other vehicle accessories, such as the power steering pump, A/C compressor, and alternator, are typically driven by one or more belts.
As we already established, the most common cause of charging malfunction warning is the alternator that does not rotate because of the torn crank pulley or drive belt.
Beware that sometimes the crankshaft pulley will not separate completely and will turn the alternator, but not fast enough. Besides, the whole assembly can seems in perfect order at first glance.
Besides these problems, the alternator itself can also fail – mostly the alternator electronics (BSD) or voltage regulator.
The Alternator is Not Working Due to Failed Drive Belt Assembly
When the drive belt comes off the belt pulley, the result is similar to that of the torn crankshaft pulley – the alternator stops working.
The Battery is Not Charged Due to Alternator Failure
If the drive belt is doing its job and you have good connections on positive and negative terminals you can check how to alternator works by measuring the voltage with a multimeter at jump start points. With the engine running the readings should be between 14V and 15V DC.
Since we have a charging malfunction warning we can expect to get the reading well below the required, so usually, you’ll see the voltage left in the battery. If you can start a car, you can expect about 11.5V to 12.5V.
However, most often than not, the charging fault is caused by other components. So, to be sure the alternator has all that it needs to operate you should first check the following:
- Good and clean connections at the charged battery
- Good and clean connections on the alternator and starter
- Good and clean connections on B+ point terminals
- Good and clean connections on engine and transmission grounds
- The tensioned and working drive belt assembly
The best approach to diagnosing a fault is by reading fault memory. If you have access to ISTA you can just follow the calculated test plan for whichever fault code appeared.
The BSD alternators are managed by an engine control unit (DME) and are not connected to the telltale light in the instrument cluster. If there’s a fault in the BSD system, the DME will usually store a fault code, but not necessarily.
So, to rule out the Intelligent Alternator Control (IGR) management error, you can disable the BSD system completely by disconnecting the Intelligent Battery Sensor (IBS) at the negative battery terminal. At this point, the alternator will start to operate as a regular alternator and charge the battery at about 14.5 volts.
Now, if you are still getting low readings → below 13.5V, you can blame the alternator for causing you all the trouble.
The most common faults with alternators are worn-out carbon brushes at voltage regulators and BSD electronics. If you look up the ETK parts catalog, you’ll quickly learn that you can’t buy internal alternator components for most BMW models.
So, if you want to go the “alternator repair” route, you’ll need to turn to aftermarket parts suppliers, who can provide the majority of the parts individually. However, this makes sense only if the alternator does not have 100k miles or more on it.
However, for some late models, like the G20 M440i with a B58D engine, you can buy the carbon brush set and replace it easily.
In my opinion, the best choice is to go with a completely new alternator from the actual manufacturer like Valeo or Denso, for example. BMW’s remanufactured alternators are commonly double the cost of the new aftermarket. This is actually one of the very few parts that I’ll personally rather buy aftermarket than a genuine BMW.
When you start repairing the old alternator you’ll find it’s usually not just one part that needs replacement.
Here’s an example of a new aftermarket alternator:
https://www.ecstuning.com/b-denso-parts/alternator/12317616119~den/
When sourcing a new alternator make absolutely sure you get the right part by comparing the part numbers and amperage of your old alternator or using the ETK parts catalog with the vehicle order matched by VIN.
Corroded B+ Terminal Points
B+ Terminal point is the place where the red battery cable passes from the inside of the vehicle to the outside. These points are known to corrode to a point that the main battery cable detaches completely on E90, E60, E82, E84, and especially the E93 convertible.
Throughout the production, some E Series, like the early E60, were covered with recall campaigns to improve corrosion protection. Besides the charging malfunction, these corroded terminals can cause countless other electrical gremlins, and in the worst-case scenario even a fire.
2010 E82 1 Series
High Resistance at Jump Start Terminal Due to Poor Contact
The jump start terminal, besides providing a jump start point, serves the same purpose as the B+ terminal at the back of your BMW. That is, connecting the main positive battery lines from the engine bay and body.
If the connection is poor at this point, the alternator will struggle to send the voltage into the battery. Unlike the B+ terminals at the back of the car the jump points rarely corrode. What I found in most cases is that nuts were not tightened enough causing the burnt contact surfaces. Why this happens, I really don’t know, but most likely someone didn’t tighten them enough during the repair.
High Resistance at Ground Points Due to Corrosion
The ground connection on your car is the connection between the minus terminal of the car battery, the car body, and the engine. It is just as important as positive battery lead.
Depending on the BMW model, the main ground connections are located between the engine mount and body, between the transmission housing and body, or both.
This ground leads complete the electrical circuit for the main battery.
Fault in Alternator Control Due to ECU Voltage Supply
As the alternator output is controlled by the DME control unit, any voltage supply problems to the DME can cause charging problems. Depending on the model, the DME voltage supply in most cases runs into a bump at faulty relays.
Although very rarely, I’ve seen a few cases where a faulty DME relay caused only a charging malfunction failure. However, in most cases, the faulty DME relay will cause many other faults like diagnostic trouble code “DME: internal error” despite the only error being a low voltage supply due to poor contact inside a DME relay.
If you suspect the problem is in the DME voltage supply, the easiest way is by measuring the voltage supply at any sensor or actuator and comparing it with the battery voltage. Of course, you can measure the supply directly at the DME connector, but the sensors are usually easier to access, but you’ll need a specific wiring diagram.
However, these types of faults will store a bunch of sensor-related fault codes. So, if you got fault codes for three or more sensors at the same time, it’s very unlikely that all sensors died at the same time. The very likely culprit is the DME voltage supply issue.
As you can see in the wiring diagram example above, the DME voltage is supplied directly via the rear fuse box and managed by DME/DDE main relay. The contact loss can happen both inside the main relay or at the B+ cable terminal connections, usually due to corrosion or they’re not tightened enough.
Blown Jump Start Point Fuse Due to Improper Jump Start
When you mix up positive and negative cables, the jump start point fuse will blow in the attempt to save other electrical components installed in your BMW. If your BMW’s engine is running, you’ll get the charging malfunction warning and when you stop the engine, you’ll be able to start it only with jumper cables.
The B+ (main battery cable) connection between the battery and the engine is cut when the fuse explodes. Jumper cables will still work to start the car, but the alternator won’t recharge the battery.
