DSC light on with steering angle code?

Nice post.
Can't say I know for sure, first time I have seen this stuff.

Seems they are comparing right and left in the bar graphs. Not every line though. It does seem you have some sort of inequality in your steering angle reading. The 18 difference might be within tolerance, where would we get that info?
What are the sensor wiper and where are they? Are those the readings from the angle sensor?
Here is what I have on DSC, you will likely have seen it all.

View attachment bmw_abs_dsc_asc_repair.pdf

View attachment DSC part 1.pdf

View attachment DSC part 2.pdf
The link to DSC_2elecctronic.pdf is no good but I cant seem to delete it sorry.

68FB said:

I don't know enough about this stuff to be sure.

Click to expand...

This made me chuckle.

A

I have this code and my research shows that the DSC module compares wheel speed sensor data to the steering angle using the logic that if the wheel speed sensors differ by a certain amount then the steering angle should vary by a certain amount becasue the vehicle is in a turn. That is how the 41 plausibility code is generated.

This is one of mine that has quite a few links about the DSC light:
http://www.m5board.com/vbulletin/e3...-discussion/205734-persistent-dsc-light-revisited.html?highlight=steering+angle

This is my original thread:
http://www.m5board.com/vbulletin/e3...52-z8-discussion/192267-dsc-light-always-question.html?highlight=steering+angle

EDIT: I thought I had linked to a TIS explanation of the steering angle operation in one of these threads but I can't find it now.

I got the same problem on my wife's E39 and it was failed steering angle sensor, PITA to replace BTW.

The LEW does compare steering angle against wheel speeds (mainly the differential side to side) and the yaw/G sensor. DSC does require the steering angle to do it's thing to the best of my knowledge, so it sounds plausible that the DSC light would be on. If you scroll down on the first screen, it will tell you more about the error.

Thank you very much for the info, gentlemen. I think I have fixed it, although time will tell.

The key was the following in the "DSC Part1.pdf" that sailor attached:
"The DSC III logic checks the plausibility of the steering angle sensor against other DSC III inputs (front wheel speeds, rotation rate, and lateral acceleration sensors). If the battery voltage is interrupted, the current steering wheel rotation is recalculated by the DSC module evaluating front wheel speeds."

So I disconnected the battery for a few seconds and went for a drive. The DSC light didn't come in and DSC works again. As suggested above, it seems the DSC was seeing an unacceptable discrepancy between the corrected steering wheel angle and the wheel speed sensors.

I took some INPA screen prints while driving AFTER the fix. (Pity I hadn't taken some before for comparison.)

Both were taken while driving straight (hands off the wheel so it self-centred). The sensor was reading about -15 degrees so the zero is off. To get it to read zero I had to turn the wheel enough I started heading for the ditch. To correct for this, the DME creates a "synthetic steering wheel angle" which it sets to zero when the 4 wheel speeds read the same. It shows as 4.39 degrees in the first screen print but it was jumping between 0 and 4 degrees. You can see it is zero in the second screen print.
From this, the DME generates the "Difference in steering angle (synthetic value - measured value)", which is the correction for the steering wheel sensor reading.

I think I must have lost this correction for some reason. A few days ago, I flattened the battery enough to only get a click from the solenoid so maybe that wiped the correction. But the light didn't start coming on until a 2-3 days after that, so I don't know.

Thanks again for the great info.

Th

So disconnecting the battery resets this system, did you notice if it cleared codes?

No, I don't think it did. I remember clearing the code with INPA after the fix.

I found this in WDS. I think the relevant part is that the steering wheel sensor is powered all the time so it can keep track of steering angle if the wheel is turned with the ignition off. So disconnecting the battery forces it to recalibrate itself.

Steering angle sensor
General
In order to function, the DSC system requires the overall steering wheel angle. The overall steering wheel angle is measured by the steering angle sensor. As the software could not be accommodated on the DSC control unit for reasons of processor capacity, a separate control unit with its own fault memory has been developed.

Arrangement in vehicle
The steering angle sensor is mounted on the steering shaft.

Operating principle
The steering-angle sensor has two potentiometers offset by 90°. The steering-wheel angle determined by these two potentiometers covers one full steering-wheel turn; each of these values is repeated after +/- 180°. The steering angle sensor knows this and counts the steering-wheel revolutions accordingly. The overall steering wheel angle is thus made up of the current steering wheel angle together with the number of steering wheel rotations. In order that the overall steering wheel angle is available at any time, uninterrupted detection of all steering wheel movements - even when the vehicle is stationary - is required. In order to achieve this, the steering angle sensor is permanently supplied with power from Terminal 30.This means that steering-wheel movements are also detected with ”ignition off”. The steering angle detected by the potentiometers remains available even after interruptions to the power supply; the number of steering wheel revolutions, however, is not. In order that the steering angle sensor remains functional after power supply interruptions, software that calculates the number of steering wheel rotations on the basis of the speed of rotation of the road wheels (and, on some models, the steering wheel being turned from lock to lock) has been integrated. This process is referred to as initialization or imposition. If imposition does not succeed by the time a speed of approx. 20 km/h is reached from a standing start, the DSC is switched to passive mode, the DSC warning lamp comes on, and a fault is recorded on the DSC control unit. The imposition process is performed whenever the ignition is switched on if the number of steering wheel revolutions is not available. Four-wheel drive vehicles are an exception to this rule: The DSC system is immediately switched to passive mode and a fault entered in the DSC control unit memory if there has been an interruption in the power supply to the steering angle sensor. In contrast with conventional-drive vehicles, the imposition process is then not aborted on reaching a specific road speed, but rather continued until the DSC is receiving correct steering angle data. At that point, the DSC warning light goes out and the DSC is operational again. In both cases, there is no fault recorded on the steering angle sensor. As an additional safety measure, the DSC control unit calculates the steering angle on the basis of the speed of the road wheels and compares it with the information supplied by the steering angle sensor. This plausibility check prevents the vehicle operating on the basis of incorrect calibration. An incorrect zero position can result from incorrect calibration or alteration of the steering geometry as a result of damage or repairs. Another safety factor is precise assignment of sensor to vehicle. During calibration, the VIN number is stored in the EEPROM and then compared with the VIN number received from the instrument cluster whenever the ignition is switched on.

Replacing the steering-angle sensor
After replacing the steering-angle sensor, it must first be coded and then calibrated using the ABS/DSC diagnostic program.

Encoding
In order to perform its internal calculations, the steering angle sensor requires model-specific data which has to be loaded onto it by means of coding.

Calibration
Calibration permanently stores the current steering wheel position as the straight-ahead position in the steering angle sensor EEPROM. Therefore, the front wheels and the steering wheel must be set exactly to the straight-ahead position before calibration. In addition, the vehicle identification number is also read from the instrument cluster and stored permanently in the steering angle sensor EEPROM. On successful completion of calibration, the steering angle sensor fault memory is automatically cleared.

Calibration must always be carried out after the following operations:

Replacement of the steering-angle sensor

Replacement of the DSC control unit

Adjustment work on the steering-angle geometry

Any work on the steering or front suspension

Voltage supply
The steering angle sensor is permanently supplied with power from Terminal 30 which also has its own fuse. In addition, the steering angle sensor also receives a power supply from Terminal 87 or, depending on model, from Terminal 15. This supply is brought via a different fuse.

Frequency counter:
When a fault is detected after ”ignition off” the frequency counter is incremented upwards by ”1”. The maximum value is ”31”.

If the fault no longer occurs during the next trip, the frequency counter is reduced by ”1”. The minimum value is ”0”.

That explanation and function description that you posted was the one I remember reading last year. Very good information right there.

I have the same code as the original poster. This happened after I started messing with the camber plates. I got the car realigned and would like to try and clear the code. I just got gt1 loaded on my laptop, but have not familiarized myself with it yet. Can someone walk me through on how to re-calibrate the steering angle sensor? Thanks!!

Simple put the steering straight disconnect the battery over night. Hook the battery back up and start the car. If that does not work your steering is off or you have more significant problems.

That sounds to easy, but I will give it a try.

My experience has shown poor battery performance to steering angle codes. M5's put a large load on the battery during sleep mode and so the batteries need to be kept up. Secondly, battery aside, this code is common on a failed steering angle sensor. Not a terrible DIY, as long as you don't mind working under the dash for over an hour. Very intelligent research by the way.

oh, and you do need to code the new one and have it aligned electronically to ensure its all correct. The computer will prefer this to a battery reset. Also will reset the tolerances that are acceptable for when you are going down the road. If its set with the battery disconnect, if at all, it will possible be pushing the limits of tolerance when driving. Anyways, curious what you end up doing.

Mine was alignment! just fixed it 2 months ago. sam issues. messed w front end. next morning had the same symptoms and only came on at 10 mpg. took it to dealer and the alignment was off by 5 degrees.

Just an update, my dsc light went away on its own after the alignment. It took roughly 200 mi's for the light to clear. I can now turn the dsc on and off with the button. It true what the say, "Patience is a virtue."

Knew it was the alignment


Sent from my iM5