This DTC sets when the final air mass adaption stored value at idle is greater than 15% above or below the calibrated threshold.
Charge air cooler (CAC) restriction
Crankcase ventilation system restriction
Crankcase ventilation system leak
Intake air system restriction
Intake air system leak
Biased mass airflow/intake air temperature (MAF/IAT) sensor
Damaged MAF/IAT sensor
Damaged exhaust gas recirculation (EGR) valve
I have run into this code several times. My common findings are leaks in the CAC tubes, aftermarket air filter assemblies and improperly installed air filters and leaks around the cover and leaking EGR valve. I know that does not necessarily help... the actual diagnostics are involved.