ADS 2 damper valve fault C1326 - Mercedes-Benz Forum
 
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post #1 of 9 (permalink) Old 05-19-2019, 08:26 AM Thread Starter
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ADS 2 damper valve fault C1326

Hi!

Today after about an hour of driving the ADS MIL went on. There were no other symptoms - ride quality wasn't affected. I had my Star laptop with me so after checking the fluid level I read the codes, and the only one present was C1326 which refers to the first (of 2) solenoid valve Y54y1 of the rear right damper valve assembly Y54, and apparently means either open or short circuit. The ADS light came back on after clearing the code. I drove another 15 minutes or so, stopped for a few minutes to unload the car, then did a couple of 5-minute drives and the light stayed off, so the problem seems to be intermittent.

Afterwards I crawled under the car and cleaned the connector of the damper valve in question with some electronics cleaner. I also removed the ADS computer and measured the resistance of the solenoids. All 4 rear solenoids were about 11.8 ohms which is within the allowed range of 10-16 ohms. A few weeks ago I already cleaned the computer and its connector.

Am I right in saying that the only possible culprits of this are the solenoid itself, the wiring and connectors, and the ADS computer? I haven't found any previous threads on the topic relating to this code, or the similar C1321-C1327, for the R129 or the W140. What I can find is the same codes happening on certain later S class cars with air suspension, not to be named here in order to not throw off search engines, but I doubt these systems have much in common.

I probably wouldn't be posting this thread at all yet before waiting to see if the problem comes back, if it weren't for the fact that I'm going on a 3-week road trip in Europe with the SL starting next Friday. So I'm in a hurry to find any possible remedies for the issue, and especially any info on whether this is likely to cut our trip short (or more likely, the car's trip). I doubt it seeing as there were no ride quality symptoms, but any thoughts?

It might be worth mentioning that despite my best efforts I haven't ever been able to notice any difference with the suspension in sport or comfort mode. The light in button goes on and in HHTWIN I can see that the current going through the valves changes in the different damping modes, but when pressing down on any of the corners, or when driving, I haven't noticed any difference. According to the MB diagnostic manual, the difference should be clear when pressing down on a corner. During the year I've had this car, I've never had an ADS fault code before.
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post #2 of 9 (permalink) Old 05-19-2019, 08:50 AM
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The difference between Sport and Comfort mode is most noticeable when the spheres are new, but you should ALWAYS be able to tell that the ride is firmer during Sport. The SL600 is not as much a real corner burner as it is a tire destroyer when taking a fast turn. The cars are a bit porky on the front end and will never make a flat turn at speed.

However, the ADS rocker does have merit which is most noticeable during highway driving. If the road becomes to poor for smooth high speed driving (bumps, cracks, expansion joints, etc.) while in Sport mode, these issues can be mitigated by returning to Comfort. It's mostly what I use the rocker for myself.

As a diagnostic for the rear damper valve, swap it with it's rear partner.

The valves themselves are seriously heavy duty and you would be among the first to report a problem with one.

In your case (based on history), I would suspect wiring and/or connectivity degradation.
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post #3 of 9 (permalink) Old 05-19-2019, 10:33 AM Thread Starter
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Thanks for the insights!

Quote:
Originally Posted by mahunt View Post
The difference between Sport and Comfort mode is most noticeable when the spheres are new, but you should ALWAYS be able to tell that the ride is firmer during Sport. The SL600 is not as much a real corner burner as it is a tire destroyer when taking a fast turn. The cars are a bit porky on the front end and will never make a flat turn at speed.
Maybe my next project during/after the summer should be replacing all the spheres. I have no idea about their history. I hope they don't become a project during our road trip

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As a diagnostic for the rear damper valve, swap it with it's rear partner.
Yes, that might make sense if this keeps happening. Though right now I don't have time to do that.

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The valves themselves are seriously heavy duty and you would be among the first to report a problem with one.
That's good to hear. I figured as much based on the lack of forum posts and similar info on the topic.

Quote:
Originally Posted by mahunt View Post
In your case (based on history), I would suspect wiring and/or connectivity degradation.
Yeah, that's what I'm thinking too. As I think I mentioned elsewhere, the other similar issue I had with the intake air temperature sometimes having an open circuit seems to have disappeared after I cleaned the ECU connectors with electronics cleaner spray. If this keeps happening, I'll try again to do the same to the ADS control unit.
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post #4 of 9 (permalink) Old 05-20-2019, 12:13 PM Thread Starter
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The light came back on today and this time the ride was clearly firmer, so it had defaulted to the hardest setting. I pulled the ADS control unit and was able to verify by measuring from the connector that the Y54y1 solenoid circuit was indeed open. So it's not the computer, at least.

I dove under the car on the garage floor, pulled the electrical connector of the damper assembly again, and tried shorting the connectors (with the control unit still disconnected) and checked for circuit continuity from the control unit side, and there wasn't any. This wasn't quite conclusive though as I wasn't able to lift the car and I had very little space to do anything, and it could be I just failed to make the connection happen.

On Wednesday I'll get the car on a lift, and will have someone to help, so I hope we can trace the issue. I'm hopeful it can still be an easy(ish) wiring or connector problem.

I noticed a local parts dealer has the rear spheres in stock. I'll pick up a pair and if this gets sorted out and we have time, I'll try to replace them too.
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post #5 of 9 (permalink) Old 05-20-2019, 02:24 PM
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The rears are the easiest of the 4 to change, but this has nothing to do with the spheres themselves.
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post #6 of 9 (permalink) Old 05-20-2019, 08:51 PM Thread Starter
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Quote:
Originally Posted by mahunt View Post
The rears are the easiest of the 4 to change, but this has nothing to do with the spheres themselves.
Yes, I know. As I said, _if_ we get the issue sorted out and have time, I'll try to do the spheres too. I don't normally have easy access to a lift so I figured I could do that as well, as I'm a bit worried about how much life the spheres have left in them. But indeed, that's a topic for another thread, as the number one problem here is clearly an electrical, not a hydraulic one.
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post #7 of 9 (permalink) Old 05-22-2019, 03:57 AM Thread Starter
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Well, well. The problem did turn out to be a wiring issue. I spent a couple of hours tracing the wire and ended up checking the passenger footwell (where e.g. the transmission control unit is). Turned out a connector was loose, and when I opened the cover under the footwell carpet, it apparently got completely disconnected. It's now reconnected and all is well!

The white connector in question and the green connector you can see behind it are both supposed to attach to the black plastic frame, but the holes on the frame are cracked and the connectors are loose. I'm guessing the connector has been disturbed by me checking the TCU connector for oil a few times.

Easy fix but the diagnosis took long enough that I decided not to go at the spheres this time. Maybe I'll get the fronts too and do all at once at some point.
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post #8 of 9 (permalink) Old 05-22-2019, 09:10 AM
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Glad to see you found the culprit.

I'd recommend doing all 4 spheres at the same time (use Febi), first the rears and then the fronts so you gain experience moving back (easier) to front (harder).

Also, if you want to cycle out as much fluid as possible (I recommend), don't press the red "lock" button to the left of the ADS raise/lower rocker before opening either bleed port. If you press the button (as recommended by the ADS II service document) you only get about a third of a liter of oil when you open the bleed port instead of almost a full liter if you don't press the button. The system will settle more with the button unpressed after replacing the spheres, but the system quickly fills the system and this flushes the most hydraulic fluid. Use a wide flat pan of some sort to catch all the dripping oil. It goes everywhere, especially when servicing the front.

Does your photo show the left side (console hump), forward (where you feet go), or right side of the passenger foot-well. It doesn't look like the above portion that is home to the HVAC vacuum block or passenger air bag, but I can't really tell.
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post #9 of 9 (permalink) Old 05-22-2019, 09:48 AM Thread Starter
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I recently changed the fluid and drained the system with the lock button pressed as per the instructions and I actually did get around a liter from each end. Weird if it's supposed to make a difference. But I'll keep that in mind. Next time I'll also take out the reservoir and clean the gunk from the bottom.

The photo shows the left side of the forward part of the passenger footwell, i.e. roughly where the left foot would go. On the bottom right is the TCU, with the left connector visible in the corner. This is (part of) what you see when you peel the floor carpeting from the forward end, and remove the plastic cover underneath it that's attached with two 10mm plastic nuts.
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