P0174 - System Too Lean (Bank 2)

P0174 is a diagnostic trouble code (DTC) that indicates the engine's air-fuel mixture is too lean on bank 2. In vehicles with V6 or V8 engines, "bank 2" refers to the side of the engine opposite to bank 1. For inline engines with four cylinders, there is only one bank, so the code refers to a lean condition on that bank.

When the engine control module (ECM) detects a consistently lean air-fuel ratio in bank 2, it triggers the P0174 code. A lean condition on bank 2 means that there is too much air relative to the amount of fuel being supplied to the cylinders on that bank. Like P0171, a P0174 code can lead to various issues, such as rough idling, reduced power, increased engine temperature, and higher emissions.

The causes of a P0174 code are similar to those of P0171 (System Too Lean - Bank 1) and can include:

1. Vacuum Leaks: Uncontrolled air entering the engine due to cracked vacuum hoses, intake manifold gasket leaks, or faulty PCV system components.

2. Faulty Mass Airflow Sensor (MAF): A malfunctioning MAF sensor can cause inaccurate air flow readings, leading to incorrect air-fuel mixture calculations.

3. Low Fuel Pressure: Insufficient fuel delivery to the engine caused by a weak fuel pump or a clogged fuel filter.

4. Faulty Oxygen (O2) Sensor: A malfunctioning O2 sensor on bank 2 can provide inaccurate data to the ECM, affecting the air-fuel mixture.

5. Exhaust Leaks: Leaks in the exhaust system before the oxygen sensor on bank 2 can introduce additional air and cause a lean condition.

6. Dirty or Clogged Fuel Injectors: Dirty or clogged fuel injectors may not spray fuel properly, affecting the air-fuel mixture.

7. Engine Mechanical Problems: Issues like low compression, a malfunctioning EGR valve, or a faulty PCV valve can lead to a lean condition on bank 2.

Diagnosing and resolving a P0174 code typically involves performing similar tests and inspections as with P0171, such as checking for vacuum leaks, testing the MAF sensor, inspecting the fuel pressure, and evaluating the oxygen sensor's performance. Due to the potential variety of underlying causes, it is recommended to seek help from a qualified mechanic to ensure an accurate diagnosis and appropriate repairs. Ignoring a P0174 code may lead to further engine damage and performance issues over time.