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

WARNING: This page is about a different variant/trim than selected.

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 Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Clear Memory Mode . and Inspection Mode Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Inspection Mode .
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 .

Fig 1: Mass And Volume Air Flow Sensor A Circuit High - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

CHECK DATA MONITOR.
1. Start the engine.
2. Using the Subaru Select Monitor, read the value in [Air Flow Sensor Voltage].
NOTE: For detailed procedures, refer to "Data Monitor". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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.
  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. Using the Subaru Select Monitor, read the value in [Air Flow Sensor Voltage].
NOTE: For detailed procedures, refer to "Data Monitor". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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. 4 - 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) (H4DO)>Mass Air Flow and Intake Air Temperature Sensor .