DTC P0103: Mass Or Volume Air Flow Sensor "A" Circuit High: Notes

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Improper idling
Engine stalls.
Poor driving performance

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode Ref. to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>Clear Memory Mode>OPERATION , and inspection mode Ref. to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>Inspection Mode>PROCEDURE .

Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CHECK CURRENT DATA .
1. Start the engine.
2. Read the value of «Air Flow Sensor Voltage» using Subaru Select Monitor.
  NOTE: For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>Subaru Select Monitor .
Is the value of «Air Flow Sensor Voltage» 5 V or more?

Yes: Go to 2

No: Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR CONNECTOR .
1. Turn the ignition switch to OFF.
2. Disconnect the connectors from the mass air flow and intake air temperature sensor.
3. Start the engine.
4. Read the value of «Air Flow Sensor Voltage» using Subaru Select Monitor.
  NOTE: For detailed operation procedures, refer to "Current Data Display For Engine". Ref. to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>Subaru Select Monitor .
Is the value of «Air Flow Sensor Voltage» 5 V or more?

Yes: Repair the short circuit of harness to power supply between ECM connector and the mass air flow and intake air temperature sensor connector.

No: Go to 3
CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR CONNECTOR .
1. Turn the ignition switch to OFF.
2. Measure the resistance of harness between mass air flow and intake air temperature sensor connector and engine ground.
  Connector & terminal
  
  (B3) No. 2 - Engine ground:
Is the resistance less than 5 Ω?

Yes: Go to 4

No: Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Open circuit in harness between ECM connector and the mass air flow and intake air temperature sensor connector
- Poor contact of ECM connector
CHECK FOR POOR CONTACT .
Check for poor contact of mass air flow and intake air temperature sensor connector.

Is there poor contact of mass air flow and intake air temperature sensor connector?

Yes: Repair the poor contact of mass air flow and intake air temperature sensor connector.

No: Replace the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>Mass Air Flow and Intake Air Temperature Sensor .