On the 2009 Chevy 3500 6.6L, the P0101 is a very straight forward code pointing to a problem with the Mass Air Flow Sensor. Inspect the air filter housing and make sure it is tight and sealed correctly. Check the air filter element and make sure it is not excessively dirty and limiting air flow. Visually inspect the air filter housing duct for for any cracks or holes. Inspect the electrical connector and wire harness for any loose, broken or damaged wires. If the visual inspection checks ok, most commonly, replacing the Mass Air Flow Sensor will solve the problem. There IS a “cleaner” for the MAF sensor, however, in experience, it’s usually not a 100% fix, and when it does work, it’s usually not for long, and MAF replacement is usually necessary.
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