ABS/ESP/BAS lights come on CLK430

[Blackbenzz]

On my 99 CLK430 my ABS/ESP/BAS lights keep turning on after driving for like 10 minutes. Its REALLY annoying! First I replaced the stop lamp switch, didn't fix the problem. Then I took it to the dealer to get a diagnosis and alot of codes came up. Under the ESP the following codes came up:
C1504 The system is switched off. Steering angle sensor is not initialized. The rotary speed test is faulty.
C1140 N49 (steering angle sensor)
C1201 A7/7s1 (BAS Release Switch)
So then he tells me to replace the steering angle sensor and he told me it was $170 at his cost and he charged me 130 for labor. I just drove home and the lights STILL com eon. SO I call him and he says it sprobably the ESP pump and its supposed to be really expensive. I've been reading the forums and hearing about replacing the battery, could thi sbe it? My Voltage test read 11.96 Anyone have any advice on what to do next? I'd really appreciate it.
On a side note, i just bought the renntech intake to complement my eisenmann race exhaust (cant wait til I get it!)