DTC P0101 With Non-GM Air Filter

Condition/Concern

A dealer may encounter a customer concern of reduced power and SES (Service Engine Soon) light illumination. Diagnostics may reveal MAF (Mass Air Flow) sensor DTC P0101.

Recommendation/Instructions

Complete the current SI diagnostics for P0101. If diagnostics were inconclusive, it's possible DTC P0101 is setting due to a Non-GM air filter. Non-GM air filters have shown a slightly higher than normal MAF reading.

The MAF sensor g/s reading can be monitored to help diagnose a P0101. Monitor the MAF sensor reading at idle with the EGR (Exhaust Gas Recirculation) off and EGR on. The EGR valve is not commanded on until the engine reaches 140 degrees Fahrenheit (60 degrees Celsius). Take an initial reading with engine temperature below 140 degrees, and one with the temperature above 140 degrees. Compare MAF g/s readings to a like vehicle with the proper A/C Delco filter, or document the readings with the non-GM filter, and then compare the readings when an A/C filter is installed. MAF sensor readings will differ depending on vehicle location/elevation.

• With engine temperature below 140°F (60°C) and EGR not on, MAF sensor g/s reading (at sea level) is at or near 40 to 45 g/s.
• With engine temperature above 140°F (60°C) degrees and EGR on, MAF sensor g/s reading is at or near 15 to 20 g/s.

Note: If the vehicle has the calibration for P0401 "Engine calibration update to address frequent occurrences of DTC P0401", the EGR will be commanded off if the engine is left idling for more than 50 seconds at operating temperature. If the vehicle has the calibration for P0401, this MAF test would have to be completed right at start up cold (engine idle stabilized), then started and checked with engine idling at operating temperature for less than 50 seconds.

Non-GM air filters have shown to run 4 to 5 g/s higher than an A/C Delco replacement air filter.

If the MAF g/s readings change substantially when the filter is swapped, evaluate the P0101 with a proper A/C Delco filter installed.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Important Information for Technicians

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

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