P0174: System Too Lean (Bank 2)

As with most diagnostic trouble codes, P0174 is a generic powertrain code, applying to most OBD-II equipped vehicles. Despite the fact this code appears across a variety of makes and models, like Ford, Chevy, Toyota, etc., repairing the error might be different and specific to each model. This code appears to be more prevalent among Ford and Chevy vehicles. Your next question, then, is likely, "How do I fix trouble code P0174?" Before we dive into the possible solutions to your current problem, it is necessary to understand the code's meaning, causes, and symptoms; then we'll address potential resolutions, but again, these might vary depending on your specific vehicle.

Check Your Check Engine Light

What Does the Code P0174 Mean?

For a vehicle to run smoothly, the air-to-fuel ratio must be maintained, and the car manufacturer of your car has installed oxygen sensors in your vehicle to monitor this ratio. Basically, the oxygen sensors in the exhaust stream sample the amount of oxygen in the exhaust and report that sample to the powertrain or engine control module. If the sample has too much or too little oxygen, then the computer makes adjustments to allow for the optimum air-to-fuel ratio. However, if the upstream oxygen sensor, located in bank 2, is continuously reading high-levels of oxygen regardless of the fuel adjustments the system thinks are being made, then the powertrain or engine control module will alert the vehicle owner by triggering the P0174 error code and illuminating the malfunction indicator lamp.

What Are the Causes?

There are several potential causes for the diagnostic trouble code P0174. For example, there could be a legitimate fuel problem. Potential fuel issues could include the rail, regulator, pump, or injectors. Also, there could be a downstream vacuum leak away from the mass air flow sensor. Last, it is also possible that the MAF sensor is faulty or dirty. It is possible that the sensor might be leaking the protective, silicone material from around the circuitry. Although, it is also possible that the use of oiled filters has caused the sensor to become over-oiled and contaminated. It is also important to note that while any one of these issues could cause the error code; it is just as likely that a combination of these problems led to the message.

What Are the Symptoms of P0299?

Fortunately, the diagnostic trouble code P0174 will probably not affect the drivability of your vehicle. However, there will potentially be several other symptoms as a result of this error message. For example, you might notice increased fuel consumption or a hesitation or surge of acceleration. You might also notice a lack of power, and you may hear what is called detonation or spark knock. These symptoms definitely speak to a lack of efficiency in your vehicle’s operation and fuel consumption. Therefore, you will want to resolve the problem as soon as possible, especially if you have noticed one or a combination of these problems.

What Can Remedy Code P0174?

While it is common to feel that replacing the oxygen sensor is the right move, perform proper diagnostic before assuming anything because the sensor may be fine. While providing specific solutions is difficult because they differ based on make and model, it is possible to provide general information that can help lead to a possible resolution. First, try cleaning the Mass Air Flow sensor. While it seems simple, it might just do the trick. Second, inspect the hoses, PCV and vacuum, and replace them if needed. Last, check the fuel filter and pressure. If you’re still having a problem, then look into getting further diagnostic testing done.

The OBD-II scanner error code P0174 problem is a generic code across several vehicles, but the solutions vary. Get proper diagnostics before replacing parts, assuming that there can only be one cause.

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