n42b20 intake manifold wiring problem

[Dakes12]

Hello,
I discovered a problem under the intake manifold of my 318ti N42b20.
The Differential Pressure Sensor it was disconnected and the wiring from intake manifold to actuator is missing... I was almost to die when i discovered..

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Here's the photo.
1 - Differential pressure sensor disconnected. I reconnect it but then car is running verry bad with sensor connected. Idle is fluctuating between 400 and 900. I think that the sensor is broken or maybe it needs the actuator connected to work properly ? I don't know.
2- The actuator wiring is missing. Others N42B20 have a 3th wire to connect the actuator. The cable which is marked with white. At my car is completely missing. I was wondering if the guy who had the car before me has cut the wire. But i din't discovered any broken wires there.
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As i am not a mechanic, i would like to ask you guys what is the role of the actuator which is not connected ?
The car is running fine, no lights on, fuel economy mixed 7.7. Everything looks fine.
I'm going to buy a new cable who have the wire for the actuator. I think that i need to remove the intake manifold.
I something hard? Can i do it by myself? Any diy will be welcome!
Thank you !!!

[MarcoZandrini]

The first step in diagnosing a problem is to scan the engine computer (DME) for codes. Yes, the differential pressure sensor may be part of the problem but other issues may be the root cause. Scan it and post them.

[Dakes12]

The first step in diagnosing a problem is to scan the engine computer (DME) for codes. Yes, the differential pressure sensor may be part of the problem but other issues may be the root cause. Scan it and post them.

The only error that i get from DME is - 00278E Differential-pressure sensor, intake manifold.
I get that error because Differential pressure sensor is disconnected. If i connect it, it will run very bad, the idle rpm is going rough and is fluctuating between 400 and 800. Like a tractor.
The differential pressure sensor works good if the actuator is not connected?
What is the role of the actuator?
I was looking for the wire diagram of the intake manifold cables but i didn't found them..
Thanks!