C0122 Mercedes Cla 45 is described as Intake Air Temperature (IAT) Circuit Malfunction. It's actually a general trouble code for a problem on IAT electrical circuit sensor, as it sends incorrect voltage input signals to the PCM. This is because the barometric pressure sensor is part of the MAF sensor. Sometimes, the MAF's sensing wire can accumulate and get covered with dirt, dust and/or oil residue, which can also lead to the error code.
Possible Causes :
Look for damage to the tank indicating impact that may have damaged the fuel pump or sender. If the scan tool has that capability, and the scan tool can operate the IMRC valves, then the problem is either resolved and a simple code clearing is all that's left or a new PCM would be called for.
Diagnostic trouble code C0122 Mercedes Cla 45 is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.
Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before C0122 Mercedes Cla 45.
Fortunately, C0122 Mercedes Cla 45 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.