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I've been getting the white and red ABC warnings for a while.
The symptoms were consistent:
Car doesn't drop, even if parked for weeks.
Start car and drive a short distance ~ 1/2 mile or so, everything is fine.
Turn off car for 10 minutes or so, start car and red warning appears.
I flushed the ABC & power steering systems with petrosyn CHF11S.
After that, the car was great for a few thousand miles, but now the same behavior has returned.
I checked fluid level is spot on, no leaks.
I ran the rodeo, during which pressure started out around 190 bar and dropped to around 130 bar. Rodeo completed with no errors.
I have a voltmeter in the car connected to the ABC pressure sensor signal where it enters the ABC control module, so I can monitor the sensor voltage during test drives.
0 bar (engine off) shows about 0.6 volts.
Good pressure (170 ~ 190 bar) shows about 3 ~4 volts.
When I do the short drive test, all is fine (3 ~ 4 volts) until engine is turned off and car sits for 10 minutes.
Upon restarting the engine, the sensor voltage shows 0.6 volts (0 bar) and I get the red warning.
If the pump is bad, I would expect to see low pressure but not zero.
If the sensor is bad, I would expect to see an abnormal voltage, maybe zero but not 0.6 volts.
If the pump pressure really was 0 bar after the restart for the drive back home, I would expect the pump to fail for lack of lubrication.
After returning home, DAS shows ABC error codes only for low pressure.
So my question is are there any other problem that might be causing these symptoms?
For example, is there some valve or pressure regulator sticking or anything else that could let the fluid circulate keeping the pump lubricated but not allow pressure to build up?
Has anyone seen a pump intermittently go from normal pressure to zero pressure like this?
I'd greatly appreciate any feedback you have to offer.
Well sorry to say but I think your pump is bad. This is exactly how my S55 acted when the pump was on it's way out. Worked ok when cold but then could not get the fluid moving again once it was stopped and restarted. You should also notice the suspension feels very strange because the valve blocks are in lock down mode to maintain the ride height as is. I use to park the car at the store and leave it running and just lock it. That got boring fast! If you wait to long it could end up costing you even more. I waited and learned a lesson, 2 new valve blocks as well. Good luck
Johan
Well I just received a new (re-manufactured) ABC pump from buyautoparts, but I still want to learn as much as I can and share the information.
So, the high pressure output from the pump goes to the pressure supply valve unit, located just behind the right front lower control arm. Attached to the this is the pulsation damper, the pressure sensor and two outputs. One output goes to a tee which splits the high pressure to the front & rear valve bodies. The other output goes to the return side, through the fluid cooler and back to the reservoir. This is to bypass any over-pressure (> 200 bar) back to the supply side. The pressure supply valve could malfunction, opening at too low of a pressure, which would return all of the pressure to the supply side even though the pump might be able to produce normal pressure.
The closed loop function works as follows:
The pressure sensor reports to the ABC control module, which controls the throttle suction valve located on the pump. The throttle suction valve opens or closes proportionally and regulates the output pressure from the pump by how much it chokes off the pump's input from the reservoir.
I've added a second voltmeter inside the cabin so I can simultaneously monitor the voltage going to the STV (suction throttle valve), as well as the pressure sensor signal voltage.
Back to the short test drive, here's what is happening:
Start engine cold, STV voltage increases towards 5 volts (control module wants pressure) and pressure sensor increases, As pressure sensor approaches 3 ~ 4 volts, STV voltage decreases. This is normal closed loop operation.
After short drive, turn engine off for 10 minutes and restart, here's what's happening:
Start engine, STV voltage increases towards 5 volts (control module wants pressure) but pressure sensor does not increase. STV voltage reaches 5 volts (control module says gimme all you got), but pressure sensor remains at 0 bar. After about 5 ~ 10 seconds of control module asking for pressure but not getting it, red warning appears, ABC goes into open loop mode, pressure sensor voltage stays at 0.6 (0 bar) and STV voltage goes to zero and stays there.
The STV valve could also malfunction in such a way that it gets voltage to open the input supply to the pump, but doesn't. So the pressure stays at 0 bar even though the pump itself might be able to produce normal pressure. Or the pressure sensor could be malfunctioning, reporting 0 bar to the control module, even though the actual pressure was normal.
Drew where is the STV valve located and also where is the pressure sensor located?
Are any two of these part of the pump assembly or separate and replaceable?
Did you install your replacement pump? and did that fix it?
The STV is on the ABC pump, if you view the pump from the front it is on the right side and protrudes from about the 2 o'clock position. The electrical connector can easily be seen attached to the end of it.
The pressure sensor is on the pressure supply valve unit, see more detail in second paragraph of #3 thread above.
Yes, I did replace the pump, flush system, rodeo, dynamic et cetera.
The ABC is perfect now.
I plan to make a monitoring system to see ABC pressure, STV voltage plus a few other things from driver's position. I'll use an arduino micro-controller which can show numbers and bargraph on a small LCD display. By comparing ABC pressure to STV voltage, the micro-controller could derive an "ABC pump health quotient". That is, how much STV opening is required to produce full ABC pressure. As the pump wears out, the STV would need to open more to get full pressure. This health quotient would need to be calculated by the micro-controller from data sampled during a non-dynamic repeatable reference state, i.e. during idle with car stationary. You could also capture and store Min & Max ABC pressures.
I'll post pics when I complete this, but it may take considerable time.
Maybe I can build several in case others are interested in one for their car.
BTW, I'm now running the Amsoil synthetic fluid instead of CHF-11S.
I've been running their euro synthetic engine oil since I got the car and I'm really pleased with it. Less expensive and better specs than Mobil 1.
I got the preferred customer membership and get a nice discount.
I've been running their euro synthetic engine oil since I got the car and I'm really pleased with it. Less expensive and better specs than Mobil 1.
I got the preferred customer membership and get a nice discount.
Interesting all this time I was terrified of putting anything else in besides Pentosin CHF-11S in there.
I'm not sure how the price difference works out though... from what I remember it's about $15 for a liter of the stuff from MB (which is 33oz) and they are asking $7 for the Amsoil 16oz bottle. Comes out to be about the same?
The STV is on the ABC pump, if you view the pump from the front it is on the right side and protrudes from about the 2 o'clock position. The electrical connector can easily be seen attached to the end of it.
The pressure sensor is on the pressure supply valve unit, see more detail in second paragraph of #3 thread above.
Yes, I did replace the pump, flush system, rodeo, dynamic et cetera.
The ABC is perfect now.
I plan to make a monitoring system to see ABC pressure, STV voltage plus a few other things from driver's position. I'll use an arduino micro-controller which can show numbers and bargraph on a small LCD display. By comparing ABC pressure to STV voltage, the micro-controller could derive an "ABC pump health quotient". That is, how much STV opening is required to produce full ABC pressure. As the pump wears out, the STV would need to open more to get full pressure. This health quotient would need to be calculated by the micro-controller from data sampled during a non-dynamic repeatable reference state, i.e. during idle with car stationary. You could also capture and store Min & Max ABC pressures.
I'll post pics when I complete this, but it may take considerable time.
Maybe I can build several in case others are interested in one for their car.
BTW, I'm now running the Amsoil synthetic fluid instead of CHF-11S.
I bought the 5 gallon pail, with the discount I think it came out to about $8 per liter.
I used about 1/3 of it for this pump replacement & flush job.
If you can find CHF-11S for $15 that's a great price, I saw it for $28 on Amazon.
Great works and brilliant idea.
With all the gauges on the dash, you will be running a forklift, . It is a great system, the ABC, anyway.
Thanks.
Howard
Hey Howard,
As you can imagine, I've been reading all the (many) ABC threads I could find.
I have say that in all those threads, nobody ever said that about it!
Hi. I know this is a very old post! I have pretty much the same issue on my 03 cl. Did you just replace the pump?
I had the red drive carefully message for a few days on and off, is usually fine in the morning, but when hot the red message comes up again. The only code I had is pressure supply low.
When I've left it for a couple of hours the reservoir is full and every time I start the car the red message comes up and diag scanner says 0 bar sometimes 1, sometimes flicks to 255 and back to 0 when starting so thought it could be the pressure sensor
Now today I need to rev the engine on start up as otherwise pressure gets to about 20bar very slowly and then the red warning comes on. When it gets up to 178bar approx it all works fine
I've done a flush etc after the first time the red light came on and now it seems worse....
On a short drive tonight revved on start as usual and abc worked fine, but then had a white visit workshop message and error code as pressure supply malfunction, but abc still worked all good, cleared code and didn't come up again....
I'm thinking pump?
Thanks for your posts, I was going the same route as you, I thought it may be the pressure sensor in the pressure supply valve and found one on ebay for cheap today, but just think I need to replace the pump really as the pressure sensor seems fine when abc works.
Finally, have you ever watched your pressure when turning off the car? Mine slowly drops from 178odd to 80odd bar quite slowly, then it drops to 0 pretty quick down from 70/80....is that normal?
Appreciate any help.... I get this post is 7 years old but you never know!
Yes, the pump turned out to be the main issue.
After replacing it, I did a flush, filter change and rodeo.
The only other improvement I've made to the ABC system since then was to cut out all of the crimped rubber hose sections of the hydraulic lines and replace them with new hoses with compression fittings.
This allows future replacement of only the flexible sections that might develop leaks (which are easily accessible) without having to replace the entire oem hydraulic lines, which are very expensive and some of them are extremely difficult to remove and replace due to their routing.
I've not had a single ABC related trouble code since that work was completed.
And I'd like to send a kind hello to Nick and Howard, who both helped me through the ABC problems.
Thank for the response, much appreciated. I guess it's a new pump for me then!
Attached are two photos of my scanner on the way to work this morning, the first is driving, the 'troughs' are obviously bumps.
The second is at idle, with me cycling the abc button, I was dubious if it was the pump or accumulators when driving, however I think the stationary test proves the pump as the pressure takes quite a while to build back up to 172bar (I know that's low, again another indicator it's the pump I think), and I'm sure pressure shouldn't drop to 135bar when just cycling the raise/lower button.
My thinking is that the accumulators ensure the car raised and then the pump tries to catch up, or could it be the other way around!? Could the pump be Okay and the accumulators gone!?
After some checking this morning, I have sort of decided the accumulators are fine, when the car is off the abc fluid level is 1/2'' above the top mark, and when running it's about 1/2'' below bottom mark, so by reading http://mercedes-abc-drive-carefully.blogspot.com/ I think the accumulators are fine, else there wouldn't be as much of a drop in the fluid when running/not.....
Pulled the engine trays and was literally pi**ing out!
It's dripping out behind the pulley /drum, so assume the front bearing seal has gone.
New pump ordered, luckily it didn't run dry so think the rest of the system should be fine.....
I flushed it all last weekend, so much have dislodged a bit of gunk which was sealing a broken o ring, oh well!
Thanks for the help
Those are interesting graphs, thanks for posting.
Did the replacement pump solve the problem ?
If you get chance it would be such useful reference to see those same graphs with a new pump. However I appreciate its hassle if a car is working, you just want to drive !
11-26-2012, 01:51 PM
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