2007 sl55 56k I have reviewed a lot of posts on ABC issues. My first attempt to resolve the stiff ride was to replace the front and rear accumulator. I also replaced a front right leaky strut unfortunately this did not help my harsh stiff ride. I ran rodeo and that works as far as i can tell. Something is not right and I’m looking for some advice. Ride way rigid. I scanned for fault codes and other than ac potentiometer the only one I got was sbs C25d8 and that one has not returned. From what i have read I would forecast faulty valve block solenoid, or another bad strut, but I don’t understand why I’m not getting any fault codes. I can’t say that any one corner is stiffer than the others, doesn’t seem so. Anybody have any ideas or experience with this

 

I saw your similar post on the SL55/SL65 section, but no replies.
I know the ABC system pretty well, but heck does anyone know it completely?
Just guessing now, but this sounds like some type of limp mode.
What scanner are you using? Does your scanner allow you (besides Rodeo) to raise and lower each corner? Tried it?
Does your scanner show the voltages for the ride level sensors while you raise and lower each corner?
Does your scanner let you perform the ABC level calibration? This ties the strut position values to the ride level sensors so that the system will know if there is a inconsistency?
I wonder if this recalibration is necessary when replacing a strut. Still strange there are no codes.
Again just guessing and hoping someone has a more definitive answer.

 

I just got a Foxwell 726, I had i980 icarsoft but it failed to see abc hydraulic suspension. I am able to raise and lower each corner The right front corner behaves differently than the other three but only after the raising and lowering was complete. After raise and lowering, the right front rose to start position by itself but the other three corners only rose after initiating the vehicle ride height button on car console. there is a calibration routine. I ran the routine but that’s it. It appeared to set and adjust on its own.

 

I just got a Foxwell 726, I had i980 icarsoft but it failed to see abc hydraulic suspension. I am able to raise and lower each corner The right front corner behaves differently than the other three but only after the raising and lowering was complete. After raise and lowering, the right front rose, concurrent with note on dash, to start position by itself but the other three corners only rose after initiating the vehicle ride height button on car console. there is a calibration routine. I ran the routine but that’s it. It appeared to set and adjust on its own. The scanner does measure
and show data. I remember 193 bar, and some numbers in millimeters Pretty sure there were voltage outputs also.

 

You said you replaced the leaky front right strut. Did you get a Mercedes strut or Arnott? When you say the strut is leaking, where is it leaking from exactly?

 

That strut has been weeping hydraulic fluid for many years, since i owned the car. I was advised to let it leak, not fix it. The seepage was evident at bottom of strut bellow the dust bellows. There were no suspensions issues until recently. The car performed impressively. As part of the recent rigid suspension problem i understood to start with accumulators but i decided to also replace that strut. I used arnott.

 

I would look at the ride height voltages at each corner as you command the corner up and down. Not sure about your scanner, but XENTRY/DAS lets you do this.
On one side of the car as the height goes up the voltages go up, but on the other side as the height goes up the voltage go down. (Who the heck would design it this way.)
Look for an inconsistency from the voltages on the same side as the same side corners go up and down. Be sure you ride height sensor is connected and working correctly.
(I once had so much trouble figuring this out I bought a used set of ride height sensors just to be sure.)
Also, have you tried just disconnecting the rear battery for a few minutes to let all modules reset?

 

Wilco. Tomorrow afternoon

 

Ok. Looking at amp draw 3 places each corner, plunger check valve/plunger valve @ neutral, raised, lowered. Data were consistent at 0/0mA neutral, 520/200mA raised, 520/-208 mA lowered, except neutral at rear left were 24/0mA.
Level data in mm was also shown. There is some minor variation there. I am curious if mm level for front is supposed to be same as rear. The rear left is not same as rear right by 9 mm. I have attached some photos. Probably too much info.
i have not disconnect/reconnected accessory battery yet

 

I have made a chart of your values for my reference.
IMHO, your rear values are different by 9mm in all positions with the right rear reading higher. Maybe that is why at level position the rear left check valve is at 24mA instead of 0mA.
IIRC the level values (in mm) are calculated from the voltages on the level sensors, not the plunger values. While the plungers (inside the shock) must also return a voltage, they are usually represented by a value between 0 (fully compressed) and 100 (fully extended). These plunger values show the true position of the corner. As I understand it, when the full calibration is done (which fully compresses and fully extended both the front and the back) by comparing the level sensor voltages to the plunger values, the system determines how to map level sensor voltages to level values in mm.

Complicated?? Seems stupidly complicated which might be why some people give up on the system. Why even have level sensors when you could just read the plunger values? Maybe the 2007+ ABC system is simpler in this way.

I learned all this when my ABC system went into fully raised, super stiff mode after replacing all the accumulators and flushing the entire system during my AMG engine swap. The Benz Ninja tried hard to help me, but all these voltages and values might have been beyond him too. So I experimented with both DAS and my Autel scanner until I understood more of it. But I still had an ABC "hard" code which would not clear. Researching the code, it could only be cleared by performing the full calibration. So obviously I tried that but it keep failing because the rear shocks would only extended to 98%, not 100. I made sure there was no binding in the suspension, even took some weight off using my hoist, removed the plungers from the shocks to check them, but it stayed at 98%. Meaning rock hard at full extension and the code would not clear.
Getting desperate, I bought two ABC controllers on eBay (maybe $60 each). Swapped one in, cleared some minor "soft" codes and everything works fine. I think one side is a bit lower than the other, but the ABC has been fine for thousands of miles. I'm hesitant to try the calibration again as a failure might give me a hard code. Well, at least I have yet another controller.

If you cannot solve this in the next few weeks, I will get values from my car. They might be off because it is not calibrated.
Good luck.

 

Mvredit: First of all, thank you for your time and effort. I’m grateful for your help. I really want to get this car working for me. Its a car i want to keep.
I have attached some screenshots that associate a voltage with pressure sensors. These seem to point also at right rear. Not sure if pointing at strut, calibration, or height sensor. Also attached are automatic calibration before and after. This can only run at neutral position. I will look some more, but I believe this is the only calibration adjustment my scanner offers. Do you know if front and rear struts are the same, esp. with regard to travel distance to top/bottom? Guess i could investigate this by checking if there is a different part no. for rear. Do you know if air induced while replacing accumulators/strut would naturally be removed by exercising level height and rodeo? Would air inhibit full strut motion?
So going forward, it seems i should do the following
1-scan the car for fault codes with a different scanner see what comes up
2-hard acu reset by disconnecting accessory battery
3-void all air from system?
3-eat pray think?
4-maybe replace right rear strut?
5-maybe replace acu?

 

Its late tonight and I am busy tomorrow. (My idea of retiring from building IT businesses was to build several auto body/repair/customization shops in the Detroit area. I visit them several times a week, but don't run them day-to-day.)
I'll try to study your screens tomorrow night.

Please confirm that you successfully performed the calibration which raised and lowered the front and rear.

 

I haven’t found where my scanner Foxwell 726 has a function to calibrate at different height levels. The function i did find is called “move to calibrated level” (automated). So i will search more thoroughly. I have friend with shop that has other scanners so i can swing by there and scan codes and attemp calibration

 

If your scanner allows level calibration, it will ask for angles at each corner. If you can't measure the suspension angles, you have to just get it the height you want and then enter the midpoint. Rear angles can be measured with a simple digital incline meter, but the fronts require a special fixture to mesh with the lower control arms.

Your numbers look pretty typical to me, but I would like to see graphs of the acceleration sensors under different driving conditions. Also, I would check and make sure that all of them are mounted securely and have correct orientation. The 2.59V reading is a little off, but not sure if it indicates a problem. They are normally very close to 2.50 with the car stationary.

 

Glad that very knowledgeable MikeJ65 chimed in. I was also wondering about the acceleration sensors, but know little about their output and had not heard of even a bad one causing a stiff ride.

@MikeJ65 When I tried a full calibration it asked for the front and rear angles as you mentioned. Not sure what they were, I looked up "typical" values and entered them. Do you have info on how to actually measure them and/or what to enter? And how do they change the calibration?

 

Is there a consensus on best scanner?

 

Yes, the consensus for these older cars will be the MB Xentry/DAS system, which in its day was used by MB dealers. It is a combination of hardware and software.
While not "officially" for sale, the hardware is readily available as a Chinese clone on eBay and Alibaba. The software is readily available as a virtual machine which will run on a Windows laptop.
Many of us have paid the BenzNinja is set this up for us. He listed exactly what clone hardware to buy and needs a dedicated "clean" Windows laptop. He remotes into the laptop, installs the software and makes it all work. That laptop must NEVER be use for any other purpose.
The system is a bit non-intuitive to use, but BenzNinja will provide assistance. The laptop I bought for this was cheap and that is likely the reason it seems a bit slow.
I have found that my high-end Autel scanner does nearly everything, but would be too expensive for just this one application. I don't know how much lower priced scanners will do.

Working on very recent model MB is more complex as it requires an AutoAuth subscription account and an AutoAuth compatible high-end scanner.

 

Weird I know, but I’m sitting in the hospital. I just had my knee replaced this morning. But yesterday I did take the car down to my friend shop. He has recent high end Autel. I ran the calibration routine associated with a strut replacement. It did not ask for any angles. It just ran, but did go through different heights around the car. It also had a load function. Both ran successfullyMy Foxwell 726 did not have these special functions. The Autel also did not find any fault codes. I ran the rodeo again for the full duration. First time I aborted after a couple minutes thinking that was normal so running the full duration may have eliminated some air. It’s a subjective assessment, but I believe the car stiffness is slightly improved, but still significantly more rigid than what I remember it being originally. Its like tire pressure at 80 psi and i feel everything so now I’m interested in this accelerometer experiment while I’m driving. Without guidance i would be doing nothing so really happy with the suggestions

 

My mind is pretty active while I’m just laying here, but I’m curious on where the accelerometers and the height position sensors actually are and how i determine their correct positions. I didn’t notice them when I put the front right strut in. I simply assumed that they were integral to the strut.

 

IIRC there are four acceleration sensors, one under the hood near each shock tower, one under the carpeting of the passenger seat and one somewhere in the back.
Mike mentioned them because a defective one could make the system "think" you are in some unusual position which is best handled with a stiff suspension.
I have never looked at their signals, but presumably Xentry/DAS or a good scanner would should their output.

But now that I think of it, can ABC really stiffen the ride without affecting height? I'm thinking it can only raise or lower the corners, although a raised corner will ride stiffer.

 

Foxwell 726 has a live data mode. I believe accelerometer output can be selected. I look forward to investigating. Might be a few days. I assume valve blocks have intake and outlet solenoids. At first i assumed if outlet was closed and inlet was half closed the strut would get stiffer w/o lengthening. Now i think that first thought wrong, pressure is pressure, stiffness should result in higher position? But then, i don’t observe high ride position with stiff ride. I am assuming abc2 has some additional method for controlling height. In any case If the outlet solenoid is stuck closed or partially closed i assume i would get fault code. But I’m not

 

OK, I’m back at it. I unplugged the accessory battery to do a hard reset but still a stiff ride without any fault codes. The scanner shows for acceleration sensors: ABC lateral acceleration sensor, left front body, right front body, right rear body. that’s 4 acceleration sensors, not indicating for left rear body acceleration sensor. Should there be one? I drove the car with a scanner showing live data and the sensors indicate normally except for the ABC lateral acceleration sensor. It had a voltage of 2.3 and 3.0 the 3.0 is outside limits. All other sensors stayed pretty normal at or about 2.5 v.


I attached two screenshots taken while driving
i am curious about abc lateral sensor data, if sensor is faulty. I am curious why no sensor for left rear body when other 3 corners are shown.

 

When Car was just sitting in the garage, all four acceleration sensors showed live data. When driving there was a number of screenshots that only showed one or two sensors so I’m wondering if the other sensors are functioning intermittently if that means they are faulty. One such screenshot example is attached above

 

You are now past my experience level. I'm now curious what my car reads; maybe I can check this weekend if the weather holds.
I would expect the acceleration values to change as you drive; if one stays at 3.00V no matter what, IMHO that indicates a faulty one.

 

I thought maybe this thread got closed so i started a new one, accelerator sensors. I attached graph screenshots there. The 3.0 reading was a snapshot it varied while driving. And your experience level is way beyond mine, nevertheless i still really want to solve the problem. I found a schematic for the electrical components of the first GEN ABC and it actually shows five acceleration sensors. My scanner only showed four and three of those were somewhat intermittent. the schematic I looked at indicates there’s a B 23/14 longitudinal acceleration sensor and I don’t get any indication for that one. The schematic says that is the one that’s behind the passenger seat perhaps somewhere in that area. I am also assuming that the sedan and the coupe both have similar abc systems. Not sure what to make of the intermittent data for three of the sensors so tomorrow I’m going to try a different scanner and see if I get something similar.