If you have a 2006 through 2010 General Motors vehicle equipped with the flex-fuel engine and you’re experiencing a check engine light illuminated and a stored code P0172, there are some quick and easy tests that you can use to diagnose the most common causes for this issue.
Fault code P0172 is stored when the PCM recognizes the fuel trim system as rich. Fuel trims can be affected by various sensor inputs, the fuel injection system itself, or even a vacuum leak. A low stored long term fuel trim percentage is also an indicator of issues.
If you have access to a scan tool with the ability to check through alcohol content percentage, view the fuel alcohol content percentage and look for abnormally high percentage amounts. An alcohol percentage above 10 to 12 percent is high for most areas of the United States.
If you suspect that the learned alcohol content reading is high, then there are a couple of tests you can do to verify this. You can also reset the adaptive fuel trims and perform an alcohol content relearn.
If you have access to a scan tool and the ability to do functional tests on the output controls of the vehicle, you can scroll over to the fuel composition reset and perform this procedure. Ensure that your fuel trims are reset to zero percentage. After this, it’s recommended to remove and clean the mass airflow wires with appropriate mass airflow sensor cleaner and check for vacuum leaks from intake manifold sources like gaskets or hoses that may affect fuel trim values.
It’s also recommended at this point to have your PCM reflashed with the latest update for your vehicle.
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What does fault code P0172 indicate?
Fault code P0172 is stored when the PCM recognizes the fuel trim system is rich. Fuel trims can be affected by various sensor inputs, the fuel injection system itself, or even a vacuum leak. A low stored long-term fuel trim percentage is also an indicator of issues.
What should be checked if the fuel trim percentage is incorrect?
If the fuel alcohol content percentage is incorrect, it is recommended to reset the adaptive fuel trims and perform an alcohol content relearn. This can be done by performing a fuel composition reset and a fuel trim reset using a scan tool with functional test capabilities. Additionally, it is recommended to clean the mass airflow wires and check for vacuum leaks from intake manifold sources.
What further action is recommended?
After performing the necessary resets and checks, it is recommended to have the PCM reflashed with the latest update for the vehicle.