In the case of OBDII codes P0170 and P0173, it is important to note that the OBDII standard does not dictate which of these various code sets must be used to (first) identify a fault how the manufacturer arrives at the compilation of data, engineering units or scaling nor the scope of parameters analyzed and used by the OEM as criteria to set the fault. As most of us are aware, the generic OBDII DTC (Diagnostic Trouble Code) structure is governed by standards, meaning each manufacturer must meet the generic standard by associating emissions-related DTCs to the (available and pre-determined) generic DTC code sets.
The OBDII Fuel Trim DTCs P0170 and P0173 are often the subject of robust online debate, some confusion as to their meaning, and further debate as to how to solve these faults in Mercedes-Benz vehicles.
