Solving the Dreaded P071 Code on a VW Jetta

P071 is the generic OBDII code for Bank 1 Lean. This means that the cars computer is adjusting for a lean condition in the car's combustion. The adjustments has gone out of range for what is considered normal by for proper emissions and fuel economy, and an OBDII fault code has been registered with the cars computer. The root cause is usually a few things:

1. A leak in the car's intake system or breather systems usually caused by a broken hose or poor connection and this results in too much air and the ECU (computer) is making adjustments to maintain stoichiometric mixture of air and gas ( 14.7:1).
2.  Not enough fuel being delivered resulting in too much air to gas mixture. This could be caused by a clog fuel filter, malfunction fuel pump or failing fuel injectors.
3. Leak in the exhaust system allows extra air into the exhaust causing the post catalytic oxygen sensor to think the engine's combustion is lean (i.e. has too much air).
4. A bad Mass Air Flow sensor is not providing the correct inputs for the ECU to set the air/fuel mix.

Disclaimer: I am not a professional mechanic. This above material is provided for educational purposes for myself and others. Your comments and feedback are welcome.