After you repair the P0171 trouble code, you need to reset it using an OBD scanner in order for the check engine light to go away.
P0171 trouble code usually comes up when there is a lean condition caused by Bank 1 (cylinders on one side of the engine).
If you have successfully repaired the P0171 trouble code and do not want to spend money resetting the code by a mechanic, read on.
1. Get an OBD2 scanning tool
Resetting the P0171 trouble code requires an OBD2 scanning tool.
An OBD2 scanning tool is a device that is used to read trouble codes, diagnose live data from the vehicle’s ECU, and erase stored trouble codes.
So before you start, make sure that you have an OBD2 scanner that is able to erase codes.
I have two scanners and both of them work just fine. I got my OBD2 scanner on amazon.com for around $90. The cheaper ones around $20 – $30 do not have the capability to erase codes, just to read them.
2. Hook up the OBD2 scanner
In order for the OBD2 scanner to be activated, you need to hook it up to the vehicle’s diagnosis port.
On most vehicles, the diagnosis port is located under the steering wheel.
However, I have seen vehicles that have a diagnosis port in the right corner of the engine bay (under the hood).
Refer to your owner’s manual if you are unable to find the diagnosis port.
Plug the connector cable from the OBD2 scanner into the vehicle’s OBD port to allow it to communicate with the vehicle’s computer and retrieve information on how the engine and other systems are performing.
3. Scan the vehicle for trouble codes
With the scanner connected to the vehicle and the key turned to the ”on” position, scan the vehicle for trouble codes.
Having in mind that all scanning tools have different designs, you will either have a ”Read” or a “Scan” button.
Mine has a ”Read” button that allows me to engage in scanning the vehicle’s trouble codes.
Scan the vehicle to determine which trouble codes are currently present.
If you have a P0171 trouble code, continue to the next step. However, keep in mind that sometimes the vehicle itself might erase the trouble code and the check engine light will turn off by itself.
4. Reset the P0171 trouble code
In order to reset the P0171 trouble code after repair, you need to select the actual trouble code from the screen (usually shown in Stored Codes) and press the button ”Erase”.
At this point, you have successfully reset the P0171 trouble code.
5. Start the vehicle
Start the vehicle and let it run for about ten minutes.
If you have successfully repaired the P0171 trouble code, after resetting it with an OBD2 scanner tool, the check engine light should not come on again.
However, if the engine is still running lean, the vehicle’s computer will detect that and will trigger the check engine light.
This means that the issue was not fixed in the first place.
Read here on how to fix the P0171 trouble code.
Resetting the P0171 trouble code after repair requires an OBD2 scanning tool that has code-erasing capabilities.
These tools usually go for around $70 to $100 which is not much compared to giving $50 to a mechanic just to reset one code.