The Diagnostic code P0174 indicates that the O2 sensor (Oxygen Sensor) located in bank number 2 has detected that a poor condition exists. The Oxygen Sensors (O2) are used by the engine to determine the air-fuel ratio, information used by the PCM (Powertrain Control Module) to inject fuel through the injectors to achieve the ideal air-fuel mixture.
The Power Train Control Module (PCM) controls the amount of fuel that is delivered to the engine; this is done by reducing or expanding the amount of this, so that the operation of the engine is the most efficient. In case the Oxygen Sensor tells the PCM that the amount of oxygen in the exhaust is more than necessary, the PCM adds more fuel, trying in this case to bring air, but this will only do so to a certain extent, since that has a limit. When the limit is reached and even the oxygen sensor indicates that the condition is poor, the Power Train Control Module (PCM) will continue to send fuel to bank 2, but it is already an amount that is more than normal. In this way, the DTC code P0174 is obtained.