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 signal on the inlet airflow through the sensor bore. The frequency varies in a range depending on engine coolant temperature (ECT) sensor 1 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.

P0102

P0103

P0102

The ECM detects that the MAF sensor is less than 3.6 g/s for greater than 3 seconds.

P0103

The ECM detects that the MAF sensor is greater than 527 g/s for greater than 3 seconds.

DTCs P0102 and P0103 are Type B DTCs.

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 the following DTCs are not set: P003A, P0047, P0048, P0106, P0403, P0405, P0406, P046C, P02E2, P02E3, P02E7, P02E8, or P02E9.

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

2. Engine running at idle, observe the scan tool MAF Sensor parameter. The reading should be between 2,400-4,400 Hz depending on the ECT sensor 1.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

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

•	Damaged components

•	Loose or improper installation

•	Restrictions or leaks in the air induction system

•	Water intrusion

•	In cold climates, inspect for any snow or ice build-up.

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 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 1 voltage circuit for a short to ground or an open/high resistance.

6. Ignition ON, test for 4.8-5.2 volts between the MAF 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. Remove the air inlet tube to the intake manifold. Refer to Exhaust Gas Recirculation Valve Cooler Replacement. Perform steps 1-6.
8. 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.

⇒	If the EGR valve inspection is normal, replace the MAF/IAT sensor.

9. If all circuits and the EGR valve test normal, test or replace the MAF sensor.

Important: You must perform the Circuit/System Testing in order to verify the integrity of the MAF sensor circuits before proceeding with the Component Testing.

To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522 to the vehicle as follows:

1. Turn OFF the ignition.
2. Connect the battery voltage supply and ground the black lead.
3. Connect the red lead to the signal circuit terminal 1 of the MAF sensor.
4. Set the duty cycle switch to Normal.
5. Set the Frequency switch to 5 K.
6. Set the signal switch to 5 volts.
7. Start the engine, observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz.

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

⇒	If the MAF Sensor parameter is within the specified range, 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.