Mercedes Actros MP 4 ACM - ACM error, low pressure Actros MP4

Hello everyone
I have tested my truck and I am getting the following error message on the tester
I have the following error
AFTERTREATMENT CONTROL UNIT IS MISSING OR BROKEN
Air pressure too low as well
Also on the dashboard the engine light is on and low power
What could be the reason, what need to be changed?
The ACM or the Nox sensor?
Thank you

Hello
ACM is installed near catalytic converter and get so hot that sometimes parts are de soldered and come loose. remove ECU and shake it and listen for loose parts.

Hi
Is ACM control unit visible on the test? If not, first of all check supply voltage on small plug of ACM control unit.
Remove the plug back cover and you will see red and brown wires - it's constant voltage from battery. On the pin "16" of the small plug (wire black/green) you can find voltage from ignition switch.

Gerri is right! That is the first thing you do.