Error code P0171 in a 2006 Toyota Camry indicates that the engine is running too lean. This means that there is too much air and/or too little fuel in the air-fuel mixture being burned in the engine. This can be caused by various factors such as:
1. Vacuum leaks in the intake system
2. Faulty Mass Air Flow (MAF) sensor
3. Clogged fuel injectors
4. Fuel pump issues
5. Faulty oxygen sensor
6. Exhaust leaks
7. Dirty or clogged air filter

To diagnose and fix the issue, you can start by checking for any visible signs of damaged hoses or loose connections in the intake system. You can also clean or replace the MAF sensor, inspect and clean the fuel injectors, check the fuel pressure, verify the condition of the oxygen sensor, inspect for any exhaust leaks, and replace the air filter if necessary.

If you are unable to find and fix the issue on your own, it is recommended to take your car to a professional mechanic to properly diagnose and repair the problem.