Basically, the DTC code P0170 OBD2 indicates that the PCM (for its acronym in English Powertrain Control Module) has detected that the fuel setting is not within the specifications that the manufacturer has set. The fault can originate because the fuel adjustment is positive or negative. Otherwise it tells us that there was a malfunction in the control that the PCM has in the air / fuel ratio.
The PCM (Power Train Control Module) receives information from the O2 sensors (Oxygen Sensor) that are used to adjust the amount of fuel the engine receives. This action that the PCM does, is known as fuel compensation.
In case the signal sent by the O2 (oxygen sensor) indicates that less fuel is needed, the PCM takes it as a negative fuel adjustment. And if the Oxygen Sensors indicate that more fuel needs to be added, this represents a positive fuel adjustment.