P0100 error and P1470 Mass inflow Sensor only has 4 sockets in plug ?

[Andyjefferies]

Hi all,
further to my previous post regarding my 2002 C Class 220 cdi going in to Limp Mode and the fan continuously running :

I have error codes as such
P1636 Electric Suction Fan unknown code
P0100 Mass Airflow Sensor
P1403 EGR open Circuit
P1470 Charge Pressure Negative control
P1180 Inlet Port Shut Off

could anyone shed any light on these faults ?

I have removed the Mass Airflow Sensor, and although it has 5 pins in the Sensor, there are only 4 pins and wires to the plug ???
How can I check whether a fault is with the Sensor or the Plug ?
Any help greatly appreciated.