Technical Description
The system is too lean on Bank 2.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles. It can affect various brands of vehicles including Ford, Lexus, Chevy, BMW, Toyota, Jaguar, Acura, Volvo, Nissan, etc. The specific repair steps may vary depending on the make, model, and engine. However, this code appears to be more common in Ford and Chevy vehicles.
Every vehicle has a PCM or ECM (powertrain/engine control module), which acts as the main computer of the vehicle. Its job is to monitor sensor readings and use that information to optimize engine performance based on current conditions.
In the case of the P0174 code, it means that the upstream oxygen sensor in Bank 2 is detecting a lean condition, indicating an excess of oxygen in the exhaust. Bank 2 refers to the side of the engine without cylinder #1 in V6/V8/V10/V12 engines.
The engine uses oxygen sensors in the exhaust stream to determine the air-to-fuel ratio. The PCM (or ECM) uses this information to adjust the amount of fuel injected by the fuel injectors. The ideal air-to-fuel ratio is 14.7:1. If the oxygen sensor indicates too much air in the exhaust, the PCM compensates by adding more fuel. However, if the lean condition persists despite the increased fuel, the PCM will trigger the P0174 code and illuminate the malfunction indicator lamp (MIL).
Here is an image of the P0174 code shown on a scanner:
It’s important to note that this code could be set due to a fueling problem, where the PCM believes it’s sending more fuel to the injectors in Bank 2, but they are not actually delivering more fuel. Other possible causes for this code are listed below.
Note: This DTC is similar to P0171, which is a lean code for Bank 1. It’s possible for a vehicle to show both codes simultaneously, especially in certain Ford models.
Symptoms
A P0174 code typically does not cause noticeable drivability issues, but there may be symptoms such as:
Causes
A code P0174 may indicate one or more of the following:
Possible Solutions
If you encounter this code, it’s important not to immediately assume that the O2 oxygen sensor is faulty and replace it. Proper diagnosis should be conducted before purchasing any parts. Following a step-by-step diagnostic process can save you money in the long run and help you gain knowledge about your vehicle.
Here are some possible solutions:
External Links
Here are a few helpful links:
