myles_everett

2007 SL550 -

My car has been having the issue of showing the "ABC Malfunction" light momentarily when going over pretty much any bump/uneven surface. The car then corrects itself (I generally feel the back rising and lowering). The red "ABC Malfunction" light goes off after a few seconds every time. Every other aspect of the ABC system functions normally. The car does not sag at all, raises instantly whenever the heigh button is toggled through the two settings, is not leaking fluid and does not have a noisy pump.

A little history on the car:
1. The ABC fluid/pump has never been serviced and the car is currently at 115,000 miles
2. I have checked fuses/relays and all are good
3. Fluid does not disappear like one would expect with a blown accumulator
4. Tires are pretty bald and I need to have them replaced asap
5. Acceleration sensors are all working as they should/recall has been performed and I swapped them out anyways to double check
6. I've been having some issues with my convenience/starter battery and I am currently putting them on a CTEK to put back in fully juiced up

Has anyone had a similar situation or any suggestions on my next course of action? I'd like to avoid paying for a STAR diagnostic because I'm stubborn and a big DIY'ER. I use the MB II Carsoft reader on this car and my others and oddly enough, the "ABC" control module will not communicate with the OBD reader. Not sure what this means.

If fully juiced up batteries/new batteries don't work, my next step was to flush the system and replace the filter, followed by tire replacement and then pulling the ABC control module and inspecting it for any kind of damage.

alexanderfoti

I wonder if you have intermittent communication with the ABC module.

Try another diag machine (preferably Xentry) and see what codes you have, I suspect an internal strut travel sensor or rear valve body wiring issue.

kbob999

The dash warning during a bump usually indicates a bad ABC accumulator/damper. Fluid would not show any indication, except a slightly lower level in the reservoir.
I'd start with the one on the pump, or the LF wheel well (older models), and see if it solves the problem. It is usually the first to go, and with that mileage I'd personally replace all of them.
Pretty easy DIY if you are inclined to do so.

bobterry99

If you sell the iCarsoft reader on eBay for $100 you can trade-up to your own Star Diagnosis system for about $200. Then you can check the ABC controller and test the accumulators.

alexanderfoti

I would have said that, but their symptoms of the car rising lowering afterwards don't match up.

mercy-me

Accumulators front or rear. Excerpt from troubleshooting guide.


See attached troubleshooting guide writeup.

Good luck,

Bob

myles_everett

Thanks for the guide! I've used it before, however, was really leaving the process of taking each wheel/liner off and inspecting and replacing the accumulators to the last resort (besides a pump replacement of course). I'm going to order the parts in the next few days and I'll post what the outcome is!

mercy-me

Myles,

Just replace the front and rear accumulators and flush the fluid as a maintenance issue. That's what I did but in my case, I was experiencing a hard ride going over bumps. I was not getting a display warning just the hard ride. I found the front accumulator intact but the rear was ruptured and full of oil. You mentioned that your system had never been serviced and the fluid level was okay however, fluid could have been added along the way during routine maintenance by the PO.

As to the pump, if the car is raising promptly then it is most likely okay. I seem to remember anything below 180 Bar pressure is cause for concern but still acceptable. You need SDS to check the pump pressure.

One final thing, the part number for the accumulators posted in the troubleshooting guide is for older R230's. Yours has the newer updated valves and accumulator setup so use the attached parts breakdown to order from and also verify with your supplier that what you are ordering is correct to your vin number. I used a random '07 SL550 vin to do the search.



One more thing. The pulsation damper on your newer model is mounted on the pump. My experience as well as others is that when it fails, you will hear a whining noise much like a failing power steering pump.

Good luck,

Bob

alexanderfoti

Accumulators are on the supply side not the return side so don't cause a hard ride like the old ADS systems.

Pulsation dampers in the older system also cause whining noise.
If you replace the one on the pump in situ it must be immaculately clean!

alexanderfoti

if the car is more than 8 years old and has done more than 80000 miles I wouldn't bother expecting them and I just would replace them.