Problems with the Electronically Controlled Damping system on RS6, C6

[Ed Chappell]

Hi,
Has anyone had experience in solving problems with the Electronically controlled damping system?
The MIL light came on after fixing the dreaded coolant pipes and changing snapped front springs without removing the DRC pipes but disconnecting the ECD plugs.
It will not reset with VCDS.

Saturday,15,June,2024,16:04:43:00251
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 7 x86
VCDS Version: 24.5.0.0
Data version: 20240429 DS355.0
www.Ross-Tech.com


Address 14: Susp. Elect. Labels: None
Control Module Part Number: 4F0 910 376 HW: 4F0 907 376
Component and/or Version: J250 DRC FahrwerH02 0020
Software Coding: 0000000
Work Shop Code: WSC 131071 1023 2097151
VCID: 64C7BC99A75B44B6C7-8030
1 Fault Found:

01769 - Sensor for Vehicle Leveling; Front Right (G289)
010 - Open or Short to Plus - MIL ON
Freeze Frame:
Fault Status: 11101010
Fault Priority: 3
Fault Frequency: 1
Reset counter: 230
Mileage: 204109 km
Time Indication: 0
Date: 2008.04.11
Time: 09:40:11

I can't find much information on exactly how the system works apart from the RS6, C6 study guide.
Removing the connector adds another fault in addition to this one in VCDS.

The left side gave similar problems but were reset after the connector pins were cleaned and the connector re-seated.

There is no label file in VCDS and very little info in the measuring blocks and I think the description in VCDS may be misleading since there is only a motor and hall sensor for the valve position in the damper.
Nothing much in the test blocks either.

It looks to be electrical so may be a broken wire.

Anyone who has had similar experiences please post or send a PM. Any advice appreciated!
Thanks

[Jim Haseltine]

Things to keep in mind:
1) VCDS is not perfect. It's a great tool but can throw misleading messages when it sees a code/model combination that Ross-Tech haven't encountered
2) the RS6 is a low volume model of the A6, a vehicle series that has a huge catalogue of possible installed optional equipment
Depending on model and equipment, an A6 can have up to 4 level sensors fitted, normally
G76 rear left
G77 rear right
G78 front left
G289 front right
These are usually linked to the headlight range control unit J431 and the air suspension level control unit J197.
Only 2 of the sensors are fitted to the RS6, front left (G78) and (I think) rear right (G77). I'm fairly certain that there's a problem with G78 on my car but the error shown in VCDS points at no comms to J197 - a unit that isn't fitted on my car. My next task is to replace G78 to see if that cures it.
If I were you I'd take a look at the connection to the level sensor on the rear axle of your car. If that makes no difference go to the front axle.

Despite the log stating MIL on, I wouldn't expect that to trigger the light, I'd expect there to be other problems highlighted in a full scan - possibly in Engine 2 as the clear codes function often won't touch them as they are echoed in Engine 1 with a message saying something like 'please check errors in engine 2' and you have to clear they from within that module.

[Ed Chappell]

Thanks for the advice Jim,
A few things to add.
The car was completely clear of all logged faults (based on full car scan including ECU2) and no warning lights before we started work on the coolant pipes and Spring replacement. So this fault is almost certainly due to something we disturbed.
The engine MIL light is not on when the engine is running but the warning icon for the electronic damping system is and does not reset. So the "MIL light on" warning in VCDS is misleading.
We did not remove the electrical plug on the front Left level sensor when we replaced the spring but we did uncouple the connecting rod from the lower suspension arm before doing the job and re-coupled it after. It is possible we damaged the sensor by moving the arm outside its mechanical range. We did not touch anything to do with the rear right sensor though.
The plan is to do some more experiments and also hopefully try to find out more about the EDC system from the wiring diagrams and VCDS WIKI.

If needed there is a local independent Audi specialist who claim to fix and recharge DRC systems that may be able to advise on the ECD system or have special diagnostic tools better than VCDS to troubleshoot these problems.
There is a very remote chance the fault may clear itself when the car is driven for a while like some the abs and steering angle faults do. But I don't hold out much hope!

[Jim Haseltine]

Ah, so the 'MIL ON' in this case is the suspension warning light on the dash.
OK, so I'd suspect the front height sensor. As far as I can understand info about the various headlight range setups on the A6, they'll still work (not 100% but they'll still work) if only one of the sensors operates.

[Ed Chappell]

Thanks Jim, I suspect you are correct.
I plan to try checking in the headlight range adjustment module with VCDS, hopefully something in the measuring blocks will show up a problem. If there is an adaption facility in there it may be worth a try since the front height of the car may be a bit different after changing the springs.
I will update the thread with the results.

[Ed Chappell]

Not solved the problem yet but this thread from Ross tech explains what is going on with Address 14, J250.
https://forums.ross-tech.com/index.php?threads/20054

Next job is to check continuity from J250 to each front N336 and N337 connector.

[Ed Chappell]

This problem has proved to be stubborn!
As mentioned by Jim H, VCDS does not report faults on suspension Module 14 quite the way you expect. Probably because module J250 is likely to be based on the air suspension controller fitted to Allroad models.
There is not much data in VCDS measuring blocks for module 14. Just entries in 1,2 and 62 but with no label file you have to guess at what it means.

If you disconnect the connectors from the front dampers you get N336+G78 faults on the front left and N337+G289 for the front right.
On the RS6, C6 these are nothing to do with the headlight levelling system sensors on front left and rear right of the car.

Nxx is the electric motor in the damper to adjust the valve and Gxx is a hall effect sensor in the damper to sense the valve position.
The basic operation is when you adjust the dampers the motor drives the valve and the sensor feeds back to the controller the valve position.

Pin allocation on the connector:
pins 1 & 2 are the 2 connections to the motor.
pin 3 is +5v for the sensor from J250
pin 4 is the output from the sensor which is a 1 KHz pulse burst, the duty cycle varies with valve position.
pin 5 is ground back through J250 for the hall sensor.

All the time the ignition is on +5v is present on pin 3 even if the damper icon is displayed with a fault.
Making up a long lead allowed us to test the front right damper by connecting it the the N336+G78 channel on J250 (front left). Ours was OK, i.e no N336 + G78 faults displayed in VCDS.

Testing the front right unit on the damper (N337 + G289) with ignition on and a oscilloscope on pins 4 and 5 showed a good waveform. Exciting the motor both forward and backwards (disconnect pins 1+2 from J250 and patch in 10 to 12v on the damper) by reversing polarity, showed the motor was good and the duty cycle from the hall sensor varied as expected. With power removed the valve stays stationary. Don't leave power on the motor too long it will overheat!

Suspicion fell on the wiring back to J250. We removed J250 which is situated behind the glove box, removed the grey connector and checked all wires for continuity or high resistance as well as shorts on Front right harness. All 5 were good.

That left J250 itself.
We found a marked difference in the waveforms fed to the motors by J250 between the left and right with the ignition on. The signal for the right was very much smaller than that appearing on the left.

The conclusion is that motor drive circuitry in J250 has gone faulty for front right, although it is a mystery why.

If you have this problem buy this connector pair to make life easier when probing https://www.ebay.co.uk/itm/304365739802

Now trying to find someone who can repair J250 or supply a used one!

[Ed Chappell]

Finally resolved the problem by replacing the J250 control module with a used one purchased from a German car breaker.
I still have more detailed notes on results obtained during the investigation. PM me if you want them.

[ATinOf]

Just spotted this post, some very important fault finding information in this thanks for sharing Ed.

Did you share your findings with the VCDS guys so they can improve the label detail?

[Bobbys3]

Finally resolved the problem by replacing the J250 control module with a used one purchased from a German car breaker.
I still have more detailed notes on results obtained during the investigation. PM me if you want them.

I have the same problem as yourself, do you have the part number for the module you replaced?

Thanks

[Ed Chappell]

All you need is in the picture below.
When buying a used one make sure the part number is exactly the same.
If I remember correctly a new one was £650+!
Good luck