Earth Connections in Motronic loom

[murat]

I was testing earth connections in the motronic harness and all looks good except for pin 30. Acording to S2 central it is a ground connection

When checking rs2 service manual I have seen this is also a part of trailer recognition/altitude sender I am not very good at schematics, Can someone check if pin 30 is earth or not? If it is not then pinout of aby and adu is not the same.

[UrS4boy]

...When checking rs2 service manual I have seen this is also a part of trailer recognition/altitude sender I am not very good at schematics, Can someone check if pin 30 is earth or not? If it is not then pinout of aby and adu is not the same.

Here is the RS2 Manual Info Re: Pin 30 in the J220 Motronic ECU. Seems to be connected to the front knock sensor, G61. But there is also the "a1" branch with the black/lilac wire that goes to a number of devices, as shown in the second diagram.

[Pat D]

It looks like a common or 0v reference for those items listed in the drawings there. A multi meter should read 12v when measuring between pin 30 and and +12v.

I haven't tested it, but it may sink to 0v (ground) only when the ecu is on.

[murat]

I tested this and it looks like its not connected to common ground.

If there is a problem with this all the connected sensors should fail imho

Am I right?

I am testing the connectivity with the "beep" mode of the multimeter

[murat]

Do you know where does this earth connection 138 connects to the earth, so i can check if it is connected?

[UrS4boy]

Do you know where does this earth connection 138 connects to the earth, so i can check if it is connected?

I think the 138 ground is one of the brown harness wires connected to the intake manifold.