SL/R230: ABC plunger sensor replacement without strut?
I read the values on the plunger travel sensors, 3 were in spec around -40 -60, the rear left was stuck at 255. I took the sensor out, cleaned the connectors, opened up the case to inspect for any visual abnormalities, everything looked ok. Put it all back together and the code was gone for a day and plunger heights read in spec. Now it is back again reading stuck at 255.
To me it sounds like a bad sensor. I started looking around to replace it but it looks like it is sold with the strut assy only ($900+). I see a couple on ebay sensor only with the plugs cut off for $200+. Any advice or recommendations without going out and buying a whole strut?
R230 04' SL600
Last edited by g0rsq; Sep 13, 2022 at 04:35 PM.
When you installed the used one, did you have to recalibrate or reprogram for the new sensor? I need to replace one out as well, and am wondering what is required. I've had mine out a couple times trying to see if reflowing solder would bring it back but so far no luck.
Thanks.


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I would like to hear the least expensive DIY "MacGyver-like" options. I was at first thinking of height sensors, as it seems the voltage is off, but I can't make the left rear strut move during calibration. That is due to the plunger problem I am thinking? I can make the voltage change in the height sensors, taking them off their mounts, so I'll look forward to any help.
Mike? Anyone?
Thanks in advance!
The Best of Mercedes & AMG


I would start with checking level, plunger, and wheel well heights at normal and fully raised levels. I think you either had an improper calibration or something is not put back together properly from the work you did.

I would start with checking level, plunger, and wheel well heights at normal and fully raised levels. I think you either had an improper calibration or something is not put back together properly from the work you did.
How can I zero out level sensors, recalibrate them, or other suggestions. I can't go on to load calibration and and such it goes to the previous crazy calibration and the cars is undrivable.



It was a car from the auction and the calibration is way off. So when I got go to calibrated level it's fouled up.
I will do your suggested measurements and respond later thus afternoon. I wish I could spend all day on it.... But I'd really have no hair left. Ha!

When the vehicle is off the heights from the fender to the center are LF 14-1/2", RF 14", LR 14", RR 13-3/4"
Last edited by JamesMBZ; Apr 18, 2024 at 05:50 PM. Reason: Additional numbers

The only DTC codes I'm getting are failure to calibration and failure of load calibrate. That's it.



I can move the RR

Do i need to run that to completion?
All so it seems to have left the heights and voltages in a better place, so I tried a calibration and it accepted the numbers but to complete the process you have to to the load calibration which lurched the car left and lower front left. However it said success, and then seemed to go to normal levels. I stopped the car. Left it over night. We'll see how it goes today, if it's driveable etc.
The plungers mm travel is a concern and I think the reason for the load calibration action. Mike?? Thoughts.... What's broken here....



I will go back into the block and make sure no oil in the connection.
The power is registering at the solonoid.
How can I know without swapping one out we there it's no good. Is there an ohm test for one?
Mike off topic briefly, 2004 SL55, the passenger seat weight sensing module can't communicate with mbstar. This srs light on. Fuse or ground, I'm going to help him today if I can... Thoughts? It was working before we did the 100A fuse in the footwell for battery issues....
Thanks man!


As far as the WSS, check the yellow connectors under the front edge of the seat. I think there are two on the passenger side, one for WSS and one for the seat belt retractor. The WSS ground point is W36, which is the passenger floor ground in front of the CAN distributor. You shouldn't need to mess with it to get to the firewall fuses, but it could have been removed inadvertently and not replaced or the wire for the WSS left off.

Latest, I checked control solonoids on the rear block. Cleaned the contacts. I was able to regain individual height control on Tuesday. Very excited about that. Then on Thursday (no activity on the SL) no control.
However, when I go to rodeo mode, I get full motion on all 4 struts.
So I stop rodeo it leaves the car in a position to go into the 3 functions required for a successful calibration. 1. Plunger calibration. I get a successful message from DAS. 2. Calibration, I get voltages in range(around 2.5) and then used - 8 and - 2,. As a result I get a successful calibration message. 3.Load adjustment - when I hit F3 the car lurches low and left ( a bit lower in the front, but it's listing left at about 30 degrees), then it normalizes to what I calibrated at and says successful load adjustment.
So I thought it adjusted and accepted all of the items needed for a successful outcome.
Well when I stop the cars engine it settles to a good locked level. But when I start it again it goes to the left listing position.
Why is the module not saving my input? Does it sound like a corrupted module N51/2?? This thing is not behaving arghhhh.
Thanks in advance,.

So when I go to individual actuations and I power the blocking solenoid and operate the control solenoids, they all do as they should except the left rear, when I hit the lower F10, it went up!
Also, it did a full rodeo with all struts in full motion. Then pitch motion with full front and rear motions.
However when I do left and right motion it only lowers on the left. So no lowering to the right.
I'm at a loss. Is this a sensor issue, a solenoid failure, an electric wiring problem on the solenoid.
lastly if i clean the plunger sensors, they pull off the top. Do i need to depressurinse the system before pulling on off?


You can bleed the pressure on the strut lines by opening the bleed valves in each wheel well. If they are rusted, don't risk twisting them off, just slowly unscrew the lines at the valve block instead of the quick connects. You won't be able to release the quick connects under pressure.

Also, the new control module showed a 9 constant 9 milliamp signal on the right rear control solenoid. So between the 2 iassues I think that's where most of the problem lies. Can the control valves cause problems and not throw codes? I'm not getting any codes except the obvious ones as I said like left front too low.
I swapped the left rear level sensor with the right side, but go significant changes, however, I still think the rear-level sensor is suspect. The reason is that the routine called "roll" makes it go center to right only, before I switched the sensor it went center to the left only. In both scenarios, I didn't get full left to right motion. After I switched the sensor and did the "roll" it went center right only. That was curious. I'll probably confirm that before we spend 80 bucks for a new sensor. By running roll and then switching it back and running roll.
Thank you very much for your insights. I've discovered that the control solenoids should give a 4-5 ohm reading on the bench to check them. Thoughts?






