Kia Troubleshooting Questions? Ask a Mechanic
The P0171 is a fairly general code that says the fuel system is running "lean". This means there is not enough fuel, too much air or a faulty oxygen sensor. So unfortunately, there is no 1-answer type of answer here and a few things will need to be tested. First, the fuel pressure will need to be tested to make sure the fuel pump is working at full capacity. If the fuel pressure checks ok, the system will need to be tested for intake air leaks and vacuum leaks. If all of these check ok, then suspect a faulty oxygen sensor. If the oxygen sensor is deemed to be the problem, it's mounted to the exhaust before the Converter. More commonly here, the oxygen sensor itself is not the problem and other items should be completely tested and ruled out before replacing the oxygen sensor. If you found this answer helpful, please help me and leave a rating using the "stars" at the top of the page or click 'accept'.Rating or accepting my answer does not cost you extra. It allows me to be credited for this Q&A.