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  #1  
Old 08-28-2016, 02:56 AM
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4.8is SLS strange operating mode after calibration attempt

Hi all,

I apologise in advance for posting yet another SLS thread. I also apologise for the long post, however I feel that some background is useful. The key behaviour is described at the end, so you can skip the background if desired.

I have a 2004 4.8is and as per all of these models I have had some interesting experiences with the selflevel suspension.
My experience started about 2 months back, when i started having SLS inactive messages popping up. Long story short, the fault was found to be caused by a faulty alternator, which was causing all sorts of errors on most body systems.
I also noted throughout this experience that the FL corner of the car would sag when the SLS was inactive, which lead me to leak test and identify pin leaks from the FL air spring.
After the alternator was replaced, the car reported no further errors for nearly a month. However, to prevent undue strain on the pump and sls system, the leaky air spring was replaced on Thursday with an Arnott unit.

I asked the workshop to perform a ride height calibration after the spring was installed, as I noted that the car never rode truly level. This was done using a SnapOn OBD scanner.
When I collected the car, I noted that the ride was very high on the rear. This levelled out as I drove home, however at the same time the car reported the SLS inactive error, accompanied by an orange TPMS light.

The workshop directed me to another BMW specialist who had a DIS scanner, as they thought perhaps the SnapOn system did not perform the calibration correctly. DIS showed an EHC 80 code for an implausible measurement from the FR corner. We attempted numerous times to calibrate the level, however eventually we did a diagnostic on the ride height sensors, which showed no change in reading from the FR corner. This test was repeated with the sensor actuator arm removed and moved manually, with no positive outcome.

This is where the odd behaviour comes in:
I had ordered a replacement sensor, thinking that this would remedy the issue, however upon leaving the shop the SLS inactive message disappeared and the car is now riding level. However, the operation of the raising/lowering system is now quite odd.
When the lower button is depressed, the lower LED flashes whilst the middle LED remains lit and the system lowers the car until I press the raise button. The car then will stop at this level and the middle led remain lit. The same is true for raising. I am not sure if the car remains at this height whilst driving - I do not wish to test it as I am cautious about placing the car in an odd ride height in case the SLS inactive message reappears.
This is unlike the system's previous behaviour, which simply raises or lowers to the preset heights.
Is the system stuck in some sort of odd mode? Or is this indicative of something more sinister? Any ideas are very much appreciated.
I have ordered a INPA OBD cable, which will allow me to diagnose the system myself, but in the meantime I am at the mercy of workshops.
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  #2  
Old 08-28-2016, 05:52 PM
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Any ideas?
I am in two minds: do I leave the system as it is, as it works just fine as far as normal driving is concerned, or do I spend the effort searching for an issue, potentially risking its operation?
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Old 08-28-2016, 07:01 PM
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BMW stole the SLS system from Range Rover when they owned them in the late 90's. Check on some of the Land Rover forums and see if they have any input...
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Old 08-28-2016, 08:58 PM
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That's not a bad idea!
I think I will wait until I have DIS/INPA then do some investigation on the system basics, such as sensor voltage and accumulator pressure.
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Old 08-29-2016, 11:20 PM
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See if this sheds light on your problem.

http://www.xoutpost.com/bmw-sav-foru...ion-light.html
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Old 08-30-2016, 12:37 AM
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SLS Inactive message is back again after 4 days absent. I will replace the front right sensor, however I still do not have my INPA/DIS to determine if it affects the issue.
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Old 08-30-2016, 03:55 AM
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I replaced the sensor. Was a very straight forward job. I took apart the old sensor to see if there was any obvious signs of damage. The insides looked to be in very good condition, so I am skeptical that the sensor was the root cause.
SLS Inactive warning and tire pressure light are still on.
I will see if I can take it to the shop tomorrow to get scanned, and perhaps recalibrated.
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Old 08-30-2016, 08:28 AM
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My X used to light up both those lights whenever the front was too low. They always went away after the car went back up to normal height. Hence, in your case, it can be an electronic issue like sensor or module thinking the car is lower than it actually is.

As for the ride height adjustment via button inside the car, it should work the way you describe....lower will flash and middle is continues until he car has reached desired position, the middle should then turn off. Either setting will reset and the car will go back to normal height once you go past a certain speed (I think it's 30km/h, but I could be wrong).

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Old 08-30-2016, 09:18 PM
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update:
This morning I was able to get INPA up and running on my Windows 10 laptop. This allowed me to scan the EHCII module, which showed the same error codes for the front right sensor, despite it being replaced.

There was also a plausibility error, however I cleared this before reading.

Looking at the voltage status of each sensor, it is clear that the module is not seeing the sensor

I inspected the loom and connector when I installed the new sensor, as well as stripping and replacing the protective sheathing. I could not identify any damage.
Therefore, the error source is either
a) damage to the sensor loom between the module and the sensor, or
b) the calibration by the first shop has somehow corrupted the module
c) the module is damaged.

The good news is that the physical system appears in good health, with good accumulator pressure, pump temperature and good control response!

I also noted the following strange numbers in the calibration screens.

The counts for the front right and rear right seem at odds with the rest of the system - does this perhaps point to an error in the calibration?

My next step is to gain access the EHCII module and do an actual measurement of the FR sensor output. This will confirm or rule out a break in the sensor loom.

If there is a voltage reading physically at the module, it indicates that my EHCII module is most likely faulty. I may responsible the shop who performed the FL air spring install and the original calibration and demand that they at least partly contribute to the cost of a new module. This error was certainly not present a week ago.
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Last edited by Beniki; 08-30-2016 at 09:51 PM.
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  #10  
Old 08-31-2016, 03:25 AM
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What a saga!! Just spend the day trying to figure out why we were not getting a signal from the front right height sensor... Turns out the parts supplier sent me the wrong part! The one I received is for a non 2 axle SLS e53, as it only outputs the height voltage on the headlight control pins ��

Will await new sensor tomorrow then recalibrate. I have a feeling the system needs to have the ginormous offset value cleared.
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