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      12-29-2012, 04:52 PM   #1
aerobod
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5e40 Fault Code & relationship to battery failure

An interesting bit of information I just deduced from resetting my steering angle sensor. Fault code 5e40 in the DSC/ABS module has a dual meaning. From a diagnostics perspective with my Bavarian Technic tool the initial error shown is "5e40 - Wheel speed sensor rear right: Signal edge missing(RDF-Typ11i).", which would point to a failing wheel sensor. An alternate description is "5e40 - Lateral acceleration signal not plausible, Offset ", this would indicate a mis-match between the steering (yaw) sensor and the perceived lateral acceleration, i.e. the steering angle sensor needs to be aligned.

So, if you have an indication from your diagnosis software that you have a rear right wheel sensor failing, it may just be a quick calibration of the steering angle sensor that is required.

From a battery failure providing a low voltage perspective, I noticed that 5e40 and various SRS codes and General Module codes were set in the fault memory. I'm not sure how the software code is written, but either a 5e40 fault code is first to be set when the module is in distress due to low voltage, or it may just be a coincidence with my car. This does explain to me why you see a general DSC/ABS failure as a symptom of a failing battery, as this error will set the ABS, DSC off and Brake Warning light yellow, as the DSC/ABS module seems to be more voltage sensitive than others.
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      12-29-2012, 05:45 PM   #2
inTgr8r
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Excellent information!!!

Thanks for posting. I suspect that I have any SAS issue and will definitely confirm this code before resetting.
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      01-07-2013, 10:48 AM   #3
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I had similar experience with battery and steering angle sensor. I just put a new one in and did some work this weekend which required disconnecting the battery several times. When I did a quick test with DIS I found 5 fault codes in the steering angle sensor. They were all caused by the battery being repeatedly disconnected. Once I recalibrated and cleared the errors, they did not return.

BTW,for anyone who needs to replace the steering angle sensor, it can be done without removing the steering column. The BMW manual states the steering column must be removed to replace the sensor, but this is not necessary, and saves about $1100 in dealer labor charges.
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      01-07-2013, 11:24 PM   #4
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What are the steering angle sensors... what's their purpose and how do you reset them?

My Head lights go up and down when I turn on the car.... that's it.


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      01-08-2013, 07:44 AM   #5
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Jstic, did you replace both sensor rings?... or are they one unit? I have never actually seen one myself. Just wondering.

Operationally, the SAS are/is two sensor rings spaced 90' away from each other... They could be individuals rings or one complete unit.
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      01-17-2013, 10:32 AM   #6
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SK, SAS is one unit. I still have the old one and will take it apart some day to see why it failed, if possible. You can buy a kit from BMW which includes the new SAS, bushings, and the special retaining bushing which holds the SAS in place. I did not go that route, the SAS was $250 at Tischer, so I bought a used one from England(from low mileage 2008 Z4) for $62 shipped. If the old one is carefully removed, all bushings can be saved. It works fine.
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      01-17-2013, 10:44 AM   #7
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Thanks for the picture. The mist is clearing....
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