Hello, welcome to 2CarPros. Let me see if I can give you a hand with this.
A Toyota PO171 is a generic code for bank 1 lean. There are several things it could be so I will give you the most common in order of cost to try to save you some money hoping it is a cheap fix.
The first is a dirty (MAF) Mass Air Flow Sensor
https://www.2carpros.com/articles/mass-air-flow-service
Second would be a leaking vacuum line or intake manifold. Visually check each line and listen for hissing, this will indicate a leak. If you find none then get a can of carburetor cleaner and carefully lightly spray all the way around the intake manifold with the engine running. If the motor speeds up at any point this indicates a leak and will require you replace the intake gasket. Please note! Carburetor clean is extremely flammable. Do not carelessly spray it everywhere. 1/2 second shots in each spot is all you need.
Third would be to replace the O2 sensor on bank 1. Here is a video on how to do that:
https://www.2carpros.com/articles/how-to-replace-an-oxygen-sensor
Let us know what you find, if this helped and if you got it fixed. If none of this works please come back and we can try some more.
Rich
Aug 11, 2019 at 12:43 PM
