I wanted to post this to hopefully help someone who has the same issue that’s been frustrating me for weeks on my 2010 Alpina D3.
Around 2 months ago my power steering warning light came on (orange steering wheel logo with an exclamation mark). At first, there didn’t seem to be any impact on the steering. It all felt normal and for about 2 weeks the light randomly turned on and off whenever it fancied.
As the issue progressed, every now and again I’d lose all power steering completely at startup, but turning the ignition off and on again kicked it back to life. I bought a new battery and coded it, just in case it was an electrical glitch. But that didn’t work.
I bought a diagnostic box but that was only giving me a generic power steering code. As the issue progressed further, at standstill, if I tried to turn the steering wheel to full lock the wheel would snap back in my hands quite violently.
I tried taking the steering angle sensor apart and cleaning the optical disc, but mine was immaculate so didn’t even need cleaning.
After seeing all my symptoms on the ECU testing website, I narrowed it down to the control module attached to the electric power steering motor which is bolted directly to the rack. I sent it off, and 2 days later the company told me no fault was found.
I had the motor returned to me and I refitted it to the car. Over the next 10 days the symptoms got worse and I lost steering assistance. The actual power steering was fine, but the electric motor is meant to kick in when at low speeds to help with parking etc, and also helps return the steering wheel to centre after exiting a turn. Those things completely stopped working for me.
I then bought an icarsoft bmw diagnostic box. This did also pick up a power steering fault but again it was too generic to tell me exactly the fault.
I downloaded the technician training booklet online which is about 20 pages on the speed dependent servitronic steering. I checked all fuses, all wiring and then used my diagnostic box to communicate with all the different modules that make up the ‘spider web’ of the power steering system. The only module I couldn’t communicate with was the power steering control module.
At this stage I sent the motor and module back for a retest at ECU testing. After a week they called and once again said they couldn’t find a fault.
At this stage I was so convinced it was the control module I asked for them to rebuild it regardless of the diagnostic outcome. They were a little taken aback and covered themselves by phone and on the invoice to say it’s my decision but they couldn’t find an issue.
I got the motor back on Thursday this week, refitted it and the power steering fault has completely gone. As I understand it the company take the circuit boards out the module, desolder most of the components and upgrade them, then give it a lifetime warranty.
The motor and control module can’t be bought as a separate part from bmw; you have to pay £2400 for a whole new rack.
The reason I’ve gone into detail about this is because I spent hours googling this issue and my symptoms. There were a huge number of bmw owners who had posted the same issue and nearly all the post threads had no ending to them showing how the owner finally solved the issue.
Hope this helps someone.