Auto diagnostics more than 1/2 volt—

Ways to Troubleshoot a P0171 Engine Code 1Attach the scan tool and start off the engine Auto diagnostics. Permit the engine to run to operating temperature. With all the engine operating, visually inspect the engine for clear vacuum leaks auto diagnostic software. Listen for hissing, which indicates a vacuum leak specifically on bank 1. Bank 1 would be the side in the engine which has the No. 1 spark plug. Refer to your service manual for this facts.2Attach your scan tool and enter the data stream diagnostic mode. Observe O2 sensor information, and MAF sensor data. Remove a vacuum line from the engine though observing the O2 sensor for a change. It ought to momentarily read lean—more than 1/2 volt—and then settle into its normal switching mode. If the sensor stays lean, replace the sensor. This is called a lazy O2 sensor and is a common cause for code P0171.3Observe the MAF sensor data. Remove the MAF sensor from the sensor housing inside the intake duct or air filter housing, using a T-15 Torx driver. Clean the MAF sensor, using MAF sensor cleaner spray. Reinstall the MAF sensor and start out the engine. Observe the MAF sensor information for any adjust in sensor reading. A dirty MAF sensor is also a common cause of a code P0171 and is usually fixed by cleaning it. If vacuum leaks and O2 sensors have been eliminated as the actual cause and cleaning the MAF doesn't fix the problem, replace the MAF sensor.