Voltage disturbances cause BSD bus problems in BMW – how to fix it?

BMW driver question – a series of problems with BSD bus components

I have an electrical problem with my car. It started a year ago. The air conditioning did not work and there were errors with the IHKA module, but it did not bother me. Recently the alternator died, but in a strange way.

Before I started fixing anything, I charged the battery, started the car and everything started working normally, even turned on the hands-free kit (Parrot CK3100 exterior), which didn’t work before (was it going to voltage?). Before I went somewhere, I checked the voltages – at startup, at rest, at maximum load and they were textbook.

The car could stand for hours and run normally, but when I went on the road, after several minutes an error popped up that the battery was no longer charged.

I immediately stopped and checked the voltages with a meter, indeed the alternator was not working. This was strange to me, because I could not find such an alternator fault on the Internet, so I started checking everything else.

IBS clamp – disconnected. I replaced the minus cables, which looked messy under the engine. I checked the battery with a specialist – efficiency at 83%, checked all fuses, checked that the pulley was OK, as well as the belts themselves. I checked that the modules under the spare wheel were not flooded. Everything was ok, so I returned the alternator for reconditioning.

They replaced all the components in the alternator, because they were already worn out – brushes, pulley and other components except the winding. And, of course, the voltage regulator. There was an error in the alternator’s computer, so the specialist who remanufactured the alternator said that the source of the problems was definitely the alternator.

The problem looked solved

I was relieved… everything was back to normal. The other day I plugged in my laptop to clear the errors and register the battery. After disconnecting it, I see a series of errors:

• IHKA – voltage – communication – air conditioning,
• DDE Alternator in ISTA,
• 4A07 Generator (Layer_BSD),
• Communication impossible – tow module and oil sensor.

I clear the errors and another error pops up – communication impossible with stop safety module, trailer communication module, even though I do not have these modules in the car. In addition, the alternator error has not disappeared even once.

So I drove up to the company that remanufactured my alternator, the specialist came out and checked the voltages with a clamp meter. He said that everything is fine with the alternator.

Other than those errors on the computer, everything is fine. Maybe just the car vibrates more at idle or I think. After installing the alternator it vibrated terribly and stopped. Perhaps I got used to it. I don’t know. It doesn’t give me a break and I drive all the time, watching the voltage, it’s in the 14.1-14.2 volt range.

Now I think something is starting to happen. Since replacing the alternator I have done about 250 km. CCC Professional navigation has already reset me from 5-7 times while driving. I will add that I have read that it is a fault in the connection of the alternator to the DDE controller or something broken on the BSD line? Thank you in advance for your reply.

The problem was with a 2005 BMW 5 E60 with a 251 hp 3 liter engine, but it may also occur in other models.

BM Cars service response on voltage disturbances and BSD bus problems

On the E60, supplying the correct voltage is very important for the proper operation of the entire vehicle. At times of reduced voltage, controllers that are not needed to keep the vehicle running are disconnected one by one to conserve voltage. Therefore, the first to be disconnected are the audio modules, navigation/phone, then the air conditioning.

In subsequent stages, the transmission (automatic) may display an error and go into emergency mode until the engine shuts down. The E60 already uses a BSD bus, on which the engine controller is connected in series with the oil level sensor, alternator and IBS clamps. The malfunction of any of these components disrupts the entire bus.

As a result of such disturbances, we can lose the measurement of the oil level in the engine, there are problems with battery charging, problems with the distribution of energy in the vehicle (IBS clamp) and the disconnection of subsequent controllers. There is also a problem with the operation of the engine itself. The DDE engine controller that is part of this bus may go into emergency mode, or engine operation will be unstable:

• rPM ripple,
• stalling of the engine,
• problems with starting,
• lack of power,
• a glowing check engine light or a drive failure message.

Finding a fault in this bus is difficult, as it requires checking all its components in turn and physically the bus itself (no short circuits, passage of the correct signal). From your description, it seems that you have already performed part of this diagnostics, it remains to check the remaining components and the bus itself.

It is also extremely rare that the engine controller itself is damaged in the part that handles the BSD bus. In that case, it remains to replace the controller with a new one or with another working one (with coding to the body).

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