Missing 401 sender earth

Hello, I'd really appreciate a bit of help as I'm struggling, I have a Audi S3 8P, after 4 years of trouble free driving my instrument cluster died, +12V was present on all pins that it should be, I checked the continuity of ground cables and found earth point 401 was open circuit, the only problem is I can't locate earth point 401 on the car. on the Audi current flow diagram it calls it "sender earth" and it says it's part of the "interior wiring harness"!
Anybody know where this is exactly?

This particular earth point is for the brake fluid level sensor, also fuel gauge, coolant level sensor, washer fluid level & the ambient temp sensor as well as the instrument cluster

Note: I've rigged up a temporary earth cable directly into the cluster so this now powers up but all the above sensors are still dead :(


Thanks in advance

http://uploads.tapatalk-cdn.com/2016...2ce0535be6.jpghttp://uploads.tapatalk-cdn.com/2016...dbc6cbd962.jpg

Cheers Paul


Sent from my iPhone using Tapatalk

Don,t know but a starting point may be door pillars area,possibly front n/s
May be a large ground at pillar that connects to a bunch of lighter grounds in the loom.
Hope you already found whats missing

Hello mate, thanks for helping, I've had the trim off the door pillars near & offside, there were 4 X earth points, all were clean and metered out perfectly :-/. I think I've checked all the earth points shown in the wiring diagram but still car is faulty [emoji26]


Sent from my iPhone using Tapatalk

My thoughts were, that where the main ground from the pillar joins the small cluster in the loom,it may be losing contact somehow.
I have seen some of these connections within the loom and and they would appear to be just wound together with a plastic cap for insulation (probably small exaggeration but).
Maybe a good wiggle on parts of the loom while someone else looks for movement in the cluster instruments may just show a problem,or confine it to a smaller area.
There are earth points under the battery tray, and I have seen reference to another in scuttle area,(Or next to cts in engine bay) (maybe another on steering column)
Hopefully someone who has more experience with same will come along soon.

Maybe forum member NHN could help.


Sent from my iPad using Tapatalk

I hope so mate, it's really doing my head in.
Ref Michael I think I know the type off connections you refer too, I've seen one behind the dashboard, it looked fine but I can check it with a meter.


Sent from my iPhone using Tapatalk

He is most active on the Audi sport forum but you can send him a pm.


Sent from my iPad using Tapatalk

Hello again PMartin,
An old post indicates an earth point in the engine bay,close to the c.t.s.(with photo) ,and this can cause the instrument cluster to go dead if in poor condition.
It would be worth checking out,although my A3 does not have this connection. Maybe yours will have it.

Ok, What do you mean by cts?


Sent from my iPhone using Tapatalk

Sorry I guess coolant temperature sensor?!


Sent from my iPhone using Tapatalk