m5board.comoholic (>1000 posts)
Join Date: Oct 2005
Location: Los Angeles
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My 2c to help the fix along
From personal experience; Circa 2008, one year or so after purchase, my 07 M6 Cabrio, had that tight steering issue upon start one morning, but it did have a transmission fault displayed. The Steering Angle Sensor was in fact the issue, The sensor alone likely didn't cause the issue, however the sensor, as it was explained to me, is checked by a module and upon catastrophic failure will tell the module there is a fault which in turn ceases the functionality of the steering control, along with a fault code in red. Transmission fault. It's possible the mechanic working on the car at that time may have misdiagnosed, or even parts troubleshot the issue. But I wouldn't rule out the sensor so quickly as a possible candidate. The cleaning DIY is sure worth a shot as is a battery check.
My symptom was inability to turn the steering wheel easily, but I did have the transmission fault that wouldn't clear no matter how many times I tried. I still have the original battery to this day.