njroute22

I feel like I'm talking to myself - but that is okay. At least there is some documentation. Like I'm creating my own Word document or something.

Anyway - I've been thinking about this yet some more.

I'm going to add the same images that I included earlier in the thread. Yes - this was once called "over-thinking things." But that is fine.

What I'm wondering about - and have no complete understanding of - is EXACTLY how the ECU decides what dampening levels to send to the four struts.

PART 1: The direct inputs to the Ride Control ECU


This is my main source of study.


As you can see from the above diagram - there are a limited set of "INPUTS" directly into the Ride Control ECU.
You have:

• Level senders (4)
• Compressor Temp Sender
• Pressure sender (from the valve block)
• Acceleration senders (3)
• And some ancillary signals from the doors (to "wake" the system up)

PART 2: Inputs via the CAN BUS


Honestly - I do not even know how to decipher this, as we do not have any "dash" info about the suspension.

And there are multiple more modules that feed into the Ride Control ECU via the CAN BUS.

Most of them seem inconsequential in regards to ride quality - with the exception of two (in my opinion).

The J220 "Motronic" Control Unit - which is more often called the ENGINE CONTROL UNIT, and the J104 ESP Control Unit - which is usually referred to as ABS or brakes. Those two seem to have the most input in terms of dampening. And in a distant third - is possible the J527 Steering Column Unit.



My thoughts about the first two are:

• I do have a fault code in the Engine ECU (for a torque mount). The resistor that is currently installed is probably bad. If I replace that with a new one - could save the day? Like I said in some post moons ago - that the suspension has been acting kooky for over 5 years.
• And as I also mentioned earlier - the parking brake is acting fishy - perhaps sending "braking pressure" to the J197 Ride Control ECU inadvertently, causing it to stiffen the ride.

Just sharing my troubleshooting mindset.

So to recap what is on my "to-do" list to try and tackle this problem:

1. Replace two front level sensors
2. Replace two front struts
3. Replace engine torque mount resistor
4. Repair or replace rear brake caliper and/or parking brake motor
5. (edit) I will also clean the ABS sensors - as I get that "ABS clicking" sometimes at low speed on dry pavement - They may be dirty

After that - I'm seriously done. I'll formally change my name to "Fred Flinstone."

dvs_dave

I had an opportunity to plug my car into VCDS and run the level control output tests. To cut to the chase, on my car the hard/soft damper currents were consistent for all 4 corners.

They all danced around +/- a few milliamps:

• 1.8A soft
• 0.05A hard

This adds more weight to your front struts being bad. There’s something wrong with the solenoid coils, or less likely, the wiring between the ECU and the strut. You should check the front strut coil resistances. What are they?

Regards how the ECU determines the dynamic damper rate; it contains damping maps that determine that, based on the various inputs. Pretty much the same way an engine ECU determines injector, spark timing, etc based on its various inputs.

njroute22

Well that is somewhat comforting. It at least confirms that my front (pair) are not acting properly. Why both at the same time and not just one or the other is disconcerting.

Is there something else besides what you mentioned that could affect just the FRONT (PAIR) simultaneously? I'll have to check - but there is some measuring block in the ride control module that lists voltages for just the front and just the rear. Mine seem to stay consistent at 4.95v - but wondering where that measurement is coming from - I suspect the ECU? Just want to cover my bases before I get cracking at the next step.

Thanks again, Dave for checking. Means a lot. It's always good to have comparisons for troubleshooting help.

dvs_dave

I checked my measuring blocks, and those two “left” and “right” were both 4.95V. Not sure what they refer to though. Also whilst stationary, the dampers are “hard” with 0.4-0.5 mA to all 4-corners.

dvs_dave

You presumably replaced both your front struts at the same time? So they’re likely both from the same bad batch that suncore must know about, given the zero questions replacements.

njroute22

Yeah - I was mistaken. left/right - not front/back.
Yes - both struts at same time. Could be a bad batch. But the fact they both act up the same (bad) way at the same time is what bugs me. Don't have my hopes up just yet.

It may be a long shot - since the issue is basically entirely inconsistent, but I wonder what effect the Engine ECU fault I have has - and what role it might play.
18284 - Valve for Torque Support Mount
I'll be fixing the resistor when I'm at the shop. Along with the front two level sensors just for good measure. Who knows if they're acting "scratchy" in some way. Can't hurt, that's for sure.

The issue that is nagging me - is if I change the struts - and the problem remains.

njroute22

This is a question for @dvs_dave or anyone else that would like to chime in.

Before I waste time and money installing two new struts that (MAY NOT) solve the problem - what do you think of this?

What if I just took the two new struts, and laid them on top of my engine - and simply unplugged just the electrical connectors from the (installed) struts - and plugged them into the new struts? And then ran the output tests?

Would that at least tell me if the solenoids inside are working and the amperage is correct? Or does that electrical connection do something else besides dampening?

Just looking for ways to avoid waste and frustration. Please share your thoughts.

njroute22

Well, here is a depressing update. I tested the new struts by disconnecting the electrical portion from the installed struts and connecting the new ones.
THE EXACT SAME POOR AMPERAGE LEVELS IN THE TESTS. Varies between 0.7a and 2.04a.

That means perhaps what? I don't know. But it appears (for now) that the struts are NOT the problem.

But I will still try the following.

• I will install yet another Ride Control ECU. Maybe the one I got on eBay was also bad? Can't make assumptions with used parts.
• While I'm there - I will try my best to check the electric connector under the dash. Maybe there are some bad connections? Dirty? Corroded?
• I will certainly try new front level sensors. Can't hurt.
• Lastly - I will also replace the resistor for the engine torque mount. You never know.

dvs_dave

Another big letdown, for sure. Try the level sensors, may as well, having gone this far. But time to really look at, and test the wiring and connections for the front struts. You’ll need to get hold of the wiring diagrams and pinouts to effectively do that. Alldata, Elsawin etc.

njroute22

I have the pinouts from Alldata. Plus, you really don't need them - as the wires are all individually and uniquely color-coded. There are only four wires I will check first. The ones to the electrical connections for each front strut.

But I will do the wiring check / possible ECU replacement (#2) only after I change the front level sensors and the engine mount resistor. Those are a bit easier - and will aid in the troubleshooting process as well. I should add that I will clean the abs sensors on each wheel - as I mentioned earlier that I get "abs clicking" at low speeds on dry pavement. I'm guessing those are dirty.

Question - Other than inspecting the wiring harness for loose connections and corrosion - what would you do? Should I conjure up some way to do a continuity test? By attaching a long wire to each connection and connect to my multimeter? Maybe rattle the wires to see if there is some kind of dis-connection? I'm certainly getting deep into troubleshooting here.

I'm a bit on the fence in terms of what would cause WEAK amperage / current being sent to the front struts exclusively and in pairs. And inconsistently as well. Sure loose connections certainly would explain some kind of inconsistency. However, it seems that one thing that IS consistent - are the values of amperage that the front struts are getting... Can't put my finger on what it would be.

One more thing I have to add is - that another "symptom" I'm still getting is that dreaded air compressor relay click. It definitely clicks on and off WAY TOO MUCH. I can't fit that bit into this puzzle, as the air springs appear to be working without any leaks. But it's still a symptom nonetheless. Could have something also to do with loose connections somewhere?