AEL VCDS connection problems

[AndyP]

My A6 has stopped connecing to VCDS, I get the message 'not connected to car'. The same cable and laptop connect to the S2 no problem. Today I've tried tracing the wires from the 2x2 plugs back to the ECU.



Black plug
Brown wire - Connects to brown wire on ECU pins 18 & 19
Red/white wire - Connects to red/white wire on ECU pin 43
Also get 12v across these when ignition is on

White plug
Green wire - Connects to Green/Black wire on ECU pin 42
White wire - Should connect to pin 27 on ECU. See pic below. Also connects to the pin shown in bottom RH corner of fusebox.



I have nothing in pin 27



The Haynes manual confirms that the K & L lines should be pins 27 & 42, even if the wire colours are different. My white wire on the 2x2 plug does not connect to anything on the ECU and I'm presuming this is the problem but where should it go??

Anybody got any other ECU schematics for the AEL?

[twoqu]

I think this a pin out but its in German!
http://www.24max.de/audifaq/TDI_STG/Belegung_EDC_A6.htm
It looks like pin 27 has the right colour code (ws) but seems to be connected to cars with auto gearbox which have assorted safety circuits wired in.
This is a wiring diagram but appears to be cobbled together. Only seems to show the K line and pin 27 going to some sort of ecu!
http://www.24max.de/audifaq/TDI_STG/A6_C4_MJ95_003.pdf

[twoqu]

Looks like pin 27 is used to control a pre heater (Steuergerät Zusatzheizung)!
Guess if you don't have one it should be unpopulated!

[twoqu]

Perhaps there is no L line!
If there are no other ring terminals on the L terminal post its not connected to anything else. The K is heavily populated. The 2X2 might just be a hangover from the ancient Motronic AAN rather than the OBD2 port.
The L line is used apparently to wake up older ecu's. Perhaps the later ecu's in the A6 did not need this.

[Joop]

Hello,

i having the same issue with the same car.There
is no voltage supply on black connector.Did you solved it?

[UrS4boy]

My A6 has stopped connecting to VCDS, I get the message 'not connected to car'.


The Haynes manual confirms that the K & L lines should be pins 27 & 42, even if the wire colours are different. My white wire on the 2x2 plug does not connect to anything on the ECU and I'm presuming this is the problem but where should it go??

Anybody got any other ECU schematics for the AEL?

That implies that VCDS once did connect to the ECU which further implies that someone stole your "27" pin and wire (highly unlikely).

Seems odd to me that 27 and 42 are the pins in question. For the AAN (and 3B and ABY and ADU) the K and L diagnostics are off Pins T55/13 and T55/55 and T55/27 is just switched power to the ECU.

[Joop]

Hello Urs4boy,
Thank you for your answer.It is still not clear what could happened with the pins if it was working correctly before i do not believe that someone stole my pin27 ecu input

[Joop]

* Ecu output(switvched power what i meant

[quattro-nick]

i'm sure that the black 2 plug is just a power suply
red/white +,brown -,i woud control this with a light blub

white 2plug,according to the wire diagram from twoqu you have 2 possibilities
with pre heater and autm gearbox or pre heater and manual gearbox
maybe is andy p 's car just a manuel without pre heater?
andy,can you confirm this?
you also can check the connections(K and L) in the auxilary relay panel,maybe there is a screw loose

[Joop]

Well the interesting that i checked with multimeter the white plug and there i can measure 9 voltage,the easiest would be to add 12 volt to the diagnostic tool but i would like to know what is the problem why there is no supply on black connector

[quattro-nick]

i found out on a other diagram that probably the power+ from the black plug comes from fuse s19(the same as for the horn) but i'm not sure
the 9v you measure on the with plug comes from the ecu internally

[AndyP]

I seem to remember mine was an issue with a cheap VCDS lead, I bought the real version so I could check the timing and it's been fine ever since.

[quattro-nick]

ooops,i have not seen that it was an old thread from you ,sorry