I have an '03 R53 with 90,000 miles. My A/C just quit last weekend, and I spent a day checking for the issue - unsuccessfully. I made an appointment with a local indy BMW shop to let them scan for chassis codes to isolate the A/C issue. On the way up to the shop, I noticed a pull to the left. This was the first time this was present. The shop scanned for codes to isolate the A/C problem, and the only code came up "steering angle sensor". They later isolated the clutch on my A/C compressor died.
Anyway, on the way back from the shop, the steering was now pulling to the right. There are no lights on the dash (DCS, low tire, etc)- nothing! All tires are within 1 psi of each other, and I've had a full alignment in the past 3000 miles. The steering wheel is perfectly centered striaght, and I have not hit any curbs or potholes. I do have Dinan lowering springs, camber plates, adjustable rear bars, but the aligmment is in spec.
I have noticed a hard right turn out of the neighborhood results in pulling to the right on straights, and a hard left will shift the steering pull to the left. I can't get it to stay neutral on steering bias.
Has anyone else had similar issues? I understand the steering angle sensor is supposed to tell the computer which way the steering wheel is pointed when a wheel locks up under hard braking to keep the car in a straight line. Does the steering angle sensor also control a "bias" on the power assist?

 

My control arm bushings are cracked. I was told when they get worse the car will pull a little, etc. Need to get new ones myself. Have someone take a look for you.