The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The MAF sensor is an air flow meter that measures the amount of air entering the engine. The engine control module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF/IAT sensor has the following circuits:

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet airflow through the sensor bore. The frequency varies in a range depending on engine coolant temperature (ECT) of approximately 2,300 Hertz at idle to near 9,000 Hertz at maximum engine load.

When engine coolant temperatures reach 60°C (140°F) the ECM commands a Rich Idle mode. During Rich Idle the exhaust gas recirculation (EGR) valve is commanded ON, and a lower frequency and g/s value will be indicated on the scan tool.

The ECM detects that the MAF sensor air flow ratio is not within a predetermined range of the calculated MAF air flow ratio for greater than 16 seconds.

DTC P0101 is a Type A DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools

J 38522 Variable Signal Generator

1. Verify that DTCs P0047, P0048, P0102, P0103, P0106, P0403, or P0405 are not set.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON Engine OFF, observe the scan tool MAP and BARO parameters. The MAP and BARO parameters should be within 4 kPa of each other.

⇒	If greater than the specified range, replace the MAP Sensor.

3. Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust.
4. Verify that leaks do not exist in the exhaust system. Refer to Exhaust Leakage.
5. Engine operating at idle; observe the scan tool MAF Sensor parameter. The reading should be between 2,300-4,400 HZ depending on the ECT temperature.
6. A WOT acceleration from a stop should cause the MAF Sensor parameter on the scan tool to increase rapidly. This increase should be from 10-40 g/s at idle to greater than 400 g/s at the time of the 1-2 shift.
7. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Important: 

1. Verify the integrity of the entire air induction system by inspecting for the following conditions:

•	A dirty or deteriorating air filter element

•	A leaking, loose, or cracked PCV pipe or seal

•	A loose or disconnected charge air cooler hose or pipe

•	A restricted or collapsed air intake duct

•	A misaligned or damaged air intake duct

•	Any objects blocking the air inlet probe of the MAF/IAT sensor

•	Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor

•	A cracked or damaged MAF sensor housing

•	Any water intrusion in the induction system

•	Any snow or ice build-up at the air cleaner, MAF or MAP sensors in cold climates

•	An intake manifold leak

•	A MAP sensor seal that is missing or damaged

•	An Intake Manifold Resonator with a leaking seal, or a cracked or broken housing

2. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
3. Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms of resistance between the MAF low reference circuit terminal 2 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

4. Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms of resistance between the IAT sensor low reference circuit terminal 4 and ground.

⇒	If greater than the specified range, test the IAT sensor low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

5. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 3 and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

6. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 and ground.

⇒	If less than the specified range, test the MAF signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the MAF signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

7. Test the charge air cooler system for leaks. Perform the Full System Air Leak Test and Induction Smoke Test. Refer to Charge Air Cooler Diagnosis.
8. Remove the Intake Manifold Tube. Refer to Intake Manifold Tube Replacement.
9. Visually inspect the EGR valve and verify the valve is in the closed position.

⇒	If the EGR valve is not in the closed position, replace the EGR valve.

10. Ignition OFF, connect the red lead of the J 38522 to the signal circuit terminal 1 at the MAF/IAT sensor harness connector. Connect the battery voltage supply to B+. Connect the black lead to ground.
11. Set the J 38522 signal switch to 5 volts, the frequency to 5K, and the Duty Cycle to Normal.
12. Engine idling, observe the scan tool MAF Sensor parameter. The scan tool MAF Sensor parameter should be between 4.950-5.025 Hz.

⇒	If the MAF Sensor parameter is not within the specified range, replace the ECM.

13. If all circuits test normal, test or replace the MAF Sensor.

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Turn OFF the ignition for 90 seconds.
5. Duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.
6. Perform the Diesel Particulate Filter (DPF) Service Regeneration.