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I should change my question as:

Should sensor/actuator ground（ground for +5V, or KL 31e) be connected to car ground (KL 31, ground for +12)

What I found out on my no start car is:

1) The sensor/actuator ground for the 5V sensor/actuators supposed to be terminal 31e, or KL 31e. This is also called electronics earth, which is sometimes marked as SENS GND on the wiring diagrams)

2) The car ground is terminal 31. This is the negative for the 12v

3) There is a big resistance between the two, like 5K Ohm.

According to the ISTA component/function descriptions, KL 31e should be connected to KL 31? But it's not clear at all.

Can anybody confirm the above. If they should, do I have a DME internal grounding problem or is there another place that the KL 31e is connected to the car ground? Like a harness and/or connection?