P0171 CODE: Causes and Fixes, System Too Lean (Bank 1)

One thing that you need to know is that there are a number of misconceptions surrounding this error code. There are also some ‘shady’ tips that others give to fix it. My job as a technician is to solve issues like this.

The diagnostic code p0171 happens when a lean mixture is detected by the front O2 sensors. This lean mixture can either be short term or long term. If the lean mixture is a short term one, it means that the fuel mixture is usually very lean. Otherwise, for long-term lean mixture, the code p0171 is registered according to an indication of the lean mixture through time.

By design, these O2 sensors typically come with a +/- 15% range. This is for the fuel mixture adjustment. If the fuel mixture is beyond this range, it is not possible for the O2 sensor to adjust the mixture. An error code is then triggered in the engine control unit. This error is then stored in the memory. If there is a lean mixture, the diagnostic code p0171 is then triggered.

There are a number of engine parts or sensors which may cause the trigger of the p0171 code, along with a lean mixture. Aside from simply focusing on p0171, it is also best to look for other sensor-related codes. Doing so will be able to provide an indication as to where you can start searching for solutions.

Here are some of the most common causes of this error:

When it comes to addressing error p0171 code, there are a number of solutions that are available. I will list down the possible solutions for the issues that were mentioned above.

Since the error code p0171 means the presence of a lean mixture in a vehicle, various sensors may cause the code. In order to diagnose this code, do the following:

Step 1: Use a car battery charger and connect it to your vehicle

This is easier to do if you have an OBD2 scanner. Check the values of the coolant temperature, MAF/MAP, intake temperature sensors, boost pressure, and make sure that they are appropriate. Replace the ones that are defective, delete the codes, and do it again.

Step 3: Check other components

After checking all sensor parameters, you can then work on checking all other parts, including intake leaks, fuel pressure, EGR valve, exhaust leaks, MAF/MAP sensor. You can also perform a thorough diagnostics of the sensors, or to check if there are damaged parts inside. For this, you need the help of a diagnostic technician for thorough coverage.