BMW X5 E53 - Bord computer / AWD issues

Question

Last week we bought a used car (BMW X5 E53 3.0L Diesel) from a private person. It looked fine and there seemed to be no major issue, only the regularly oil service was due.

On our way home the 4x4 warn light went on. Despite of that we recognized following issues in the next days:

• the all wheel drive doesn't work. The front wheels sometimes jerk while steering hard. Steering also causes a click sound.
• the right right rear turn signal sometimes fails
• the bordcomputer display sometimes stays black (black with back light) for some minutes after engine start / when this happens sometimes the radio doesn't work, too. Update: This seems to be caused by pre-heater.
• the navigation sometimes fails (there is no TMC, too but this might be coincidental)
• the engine might lose some oil, but not much. We had the car tested for major issues at the Association for Technical Inspection (TÜV) but they didn't find this critical.
• the tires are worn out and have to be replaced next season.
• Update: the PDC doesn't work. It worked for a short time after I cleaned the sensors. This could be because of the dirty streets, bad weather these days. This was caused by the license plate.
• Update: the adaptive headlight doesn't work. (which can be caused by the DSC error as mentioned in the answers)

Apart from this the car drives fine. It switches gears smoothly and other electric systems seem to work.

Our favorite car mechanic go through the error logs but couldn't find something specific. He told us to go to a BMW service and let it be tested there. This was BMW's log: (if necessary I could try to translate it, just tell me.)

Questions: Which components could be causing all of this? We'd like to change them ordered by probability of being the root cause and lowest repair cost first (as this might be less expensive as a lawyer suing the seller of the car, as we probably lose the case).

Is it dangerous to drive the car in this state?

It is such a beautiful car with which we felt blindly in love but we cannot afford some thousands of euros just to find the error cause. We had learned our lesson on the hard way. I hope my request was understandable and fits the requirements of this site.

Update: this morning I started the car. Then I switched gear on 'D' (driving mode) and the engine died and the red warn lights for battery and oil went on. I restarted it and it worked fine, despite of the bordcomputer (and radio) which stays black for almost the whole drive (30min). Some minutes before the arrival it went on and the radio started working. May this be because of temperature outside (~ -5°C)?

Update 2: We drove the car to our mechanic yesterday, he'll do both oil changes and will look if he can find any error causes. He won't do the electrics though. We will return to BMW service for that. Therefore could you might give me some advice where they'll have to look at first, so that they won't waste to much of their time and our money? I observed, the bordcomputer seems only to stay black after the pre-heater was on before. About 10-20min after pre-heater stops, the bordcomputer display will work again. Why would it overheat?

Update 3: Our favorite mechanic changed both oil changes and 'taught' (anlernen) the steering angle sensor and the 4x4 error disappeared for a short time. After engine restart, it was on again. Today first start and gear switch to 'D' engine again failed, but now just the battery light went on. We well let our 'track be set' (Spur einstellen). If this doesn't help, we'll get a new sensor. Anyway, he told us that the battery is dying which might have cause the electric issues. (BMW service told us the battery was okay, so we didn't thought about that anymore.) I ordered a new one. I'll update the results a soon as we changed it. Thank you all for helping. <3

Update 4: We changed the battery and now all electric issues seem to be gone. Also we changed the steering angle sensor and let it be initialized by official BMW service (although a different branch) and until now, the 4x4 warn light disappeared. Tomorrow, we'll let the track be set and the thermostat of cooling water (?) be replaced and then we are done for now. There is still the issue marked in the error log about the glow plugs. Our mechanic told us they influence the start up of the car and as long as it starts we might delay it as a repair would cost about 1000€ which is to much for us now, as we have to buy new tires until Easter. My personal resume from this is: if it looks too good to be true, it's probably not true.

Answer 1

Please take the following text with a grain of salt as this is just an interpretation of a complex problem from a random dude on the Internet

• The steering angle sensor issue (DSC) is the most dangerous (and probably expensive) issue as your road safety depends on it. Perhaps it is caused by the later mentioned electrical issue, but this is something critical and you need to be sure about it. The same for the brake force control (IKE). Edit: Those systems are designed with a mechanic override, so in case of a electronic fault you can still steer and brake, albeit without any electronic assistance (ABS, ESP, perhaps Power steering etc.)
• The needed oil change on the distribution gearbox (VTG) is also pressing as it increases wear on the transmission (and a transmission breakdown is the economic write-off in your situation).
• The glow-plug related errors indicate a past electrical fault, unless you experience starting problems on cold weather you could treat them with less priority (or even ignore them as the fault is not present at the moment).

The rest of the errors and symptoms indicate some fault onto the electrical system (distortion onto the bus or noise/other problems on the power supply). If you are really lucky there is only a easily spotted faulty cabling or old battery, but you definitely need the assistance of an competent vehicle electrician.

Competent means: Not one of those that blindly replace parts until the problem disappears.

Update: Perhaps you want to go to some competent, independent vehicle electrician first? The dealerships have often the tendency to prefer replacing just entire part groups as it still solves the problem somehow, it does not require much experience and improves cash-flow. Should they replace the entire involved electronics incl. wiring harness it would be financial overkill

Answer 2

Here are my observations (kudos to Myself for providing translations):

1. DSC: Lenkwinkelsensor Versorgung [Steering angle sensor power supply]
   LWS: Schleiferfehler (Ableichbetrieb) [Slider error (calibration)]

   It seems that the steering angle sensor is not being supplied power as it should. This error was set about 500 km prior to the vehicle's reported current mileage.

   This is the source of your steering-wheel-clicking sound. I know because I had a similar experience on my E39 BMW (though I never got round to fixing it).

   It appears that this fault also explains the strange behaviour of the Dynamic Stability Control. Weather-permitting, I would strongly recommend you to disable the DSC until this issue is resolved. If I remember well, the steering wheel clicking sound should disappear when DSC is deactivated.

   The code could mean one of two things:

   • The sensor is kaput due to an internal open circuit (likely, given the well-documented failure of this sensor)
   • The sensor's power supply wiring has an open (not likely, but remains a possibility)

2. DDE: Elektrischer Zuheizer, Ansteuerung [Supplemental electrical heater, control]
   DDE: Glühkerze Zylinder X, Ansteuerung: Glowplug cylinder X, control

   This appears to be a separate issue, stored around 130 km prior to the vehicle's reported current mileage. It looks like the glow plug control is not as it should be.

   There isn't enough information here to guess what could be wrong here, and my familiarity with diesel systems is very limited.

3. The status of the other error codes is unknown (except for the transfer box oil which Myself has already addressed in his answer). They are not critical to the functionality of the vehicle.