The 4 pin sensor is a VDO 213/4/2 and the connector has the part number 1-965526-1 A, which it seems was made by TE Connectivity but is no longer available on their site. Anyone have another source? Or does anyone have a defective wiring harness with this connector?

Mercedes uses the same connector with the part number 210-540-47-81. I'm off to the Mercedes dealer tomorrow...

I think I have figured out the details to adapt my 2001 engine to my 2000 car. Most of this information is stated earlier in this thread but the specifics were not clear.
First, where is the X3/1 30 pin connector that needs to have 2 wires added to it?
Here it is in its natural habitat in the trunk.

http://986forum.com/forums/uploads02...1692997299.jpg

Here is a picture of the connector that is on the original wiring harness of my 2000 S, on the seized engine that was removed.

http://986forum.com/forums/uploads02...1692997318.jpg

This is the connector on the engine harness of the 2001 replacement engine I installed.

http://986forum.com/forums/uploads02...1692997340.jpg

Pins 29 and 30 are in the top row of the pictures on the left. As you can see the 2001 connector has pin 29 empty... this is the signal that is missing to make the temperature gauge function.

The engine currently has a 2 pin temperature sensor and the matching 2 pin connector in the wiring harness.
So I have a 4 pin temperature sensor (from the original engine), a 4 pin connector with the 4 female pins (bought from Mercedes Benz for way, way too much money).
The 4 pin connector has to be installed as follows:
Pin 1 - the blue/pink wire that is on pin 1 of the current (2 pin) connector.
Pin 2 - a new wire that will be run into the trunk and connected to the brown wire in position 30 of the 30 pin connector
Pin 3 - a new wire that will be run into the trunk and connected to position 29 of the 30 pin connector. A female connector is needed because that position is empty in the 30 pin.
Pin 4 - the brown/pink wire that is on pin 2 of the current (2 pin) connector.

I plan in drilling a hole in the rubber grommet to route the new wires into the trunk.

I have not as yet done this conversion but am confident that I have it figured out. I will post the results when it is completed.

While looking at my old wiring harness I noticed that there is another 4 pin connector the same as the one for the temperature sensor that is on the bank 2 knock sensor (I think). That could be a source for a connector if you have a damaged wiring harness that can be sacrificed instead of spending $$$$$$ at Mercedes Benz.

The sensor and connector are installed with the wiring as outlined in the previous post... and it works!

http://986forum.com/forums/uploads02...1693768085.jpg