[panzer dragoon]

To provide the best possible combination of driveability, fuel economy, and emission control, a closed loop air and fuel metering system is used. While in closed loop, the PCM monitors the HO2S 1 signal and adjusts fuel delivery based upon the HO2S signal voltage. A change in the fuel delivery will be indicated by changes in the long and short term fuel trim values. The fuel trim values can be monitored with a scan tool. Ideal fuel trim values are approximately 0 percent . If the HO2S signals indicate a lean condition, the PCM will add fuel, resulting in fuel trim values of more than 0 percent . If a rich condition is detected, the fuel trim values will be less than 0 percent , indicating that the PCM is reducing the amount of fuel delivered. If an excessively lean condition is detected, the PCM will set DTC P0171.

Hopefully it was just a bad case of fuel and the code goes away.