The P0171 code indicates that the oxygen (O2) sensor on bank 1 sent a signal to the engine control module that the air-fuel mixture is too lean to be corrected. The O2 sensors have the ability to correct a fuel mixture of +-15%. If it needs to be corrected more than that, the P0171 code will be stored.

The P0171 error code tells you that a lean condition exists, which means the ratio of air to fuel is off, and there’s too much air in the system. In this article, we’ll break down the symptoms, causes, and possible solutions for this error code so you can get your Volkswagen properly functioning again.

A Code P0171 or system too lean bank 1 means either too much oxygen or too little fuel in the exhaust. This is a ‘lean’ condition or a ‘low fuel trim’ code. The P0171 OBD-II code indicates that the fuel system on the first bank of the engine is weak or that a vacuum leak exists near this side of the engine.

If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replace the air filter and clean the air flow meter. If the problem persists the front oxygen (O2) sensor may need to be replaced.