DTC P0201: Cylinder 1 Injector "A" Circuit: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

• Improper idling
• Poor driving performance

Wiring diagram: 

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

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK POWER SUPPLY TO FUEL INJECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from fuel injector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between fuel injector connector and the engine ground.

      Connector & terminal 

      DTC P0201; (E5) No. 1 (+) - Engine ground (-):

      DTC P0202; (E16) No. 1 (+) - Engine ground (-):

      DTC P0203; (E6) No. 1 (+) - Engine ground (-):

      DTC P0204; (E17) No. 1 (+) - Engine ground (-):

   Is the voltage 10 V or more?

   Yes:  Go to  2

   No:  Repair the harness and connector.

   NOTE: In this case, repair the following item:

   • Open circuit in harness between main relay and fuel injector connector
   • Poor contact of main relay connector
   • Poor contact of coupling connector
2. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
   3. Measure the resistance between fuel injector connector and engine ground.

      Connector & terminal 

      DTC P0201; (E5) No. 2 - Engine ground:

      DTC P0202; (E16) No. 2 - Engine ground:

      DTC P0203; (E6) No. 2 - Engine ground:

      DTC P0204; (E17) No. 2 - Engine ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  3

   No:  Repair the short circuit to ground in harness between ECM connector and fuel injector connector.

3. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR  .

   Measure the resistance of harness between ECM connector and fuel injector connector.

   Connector & terminal 

   DTC P0201; (B134) No. 10 - (E5) No. 2:

   DTC P0202; (B134) No. 11 - (E16) No. 2:

   DTC P0203; (B134) No. 12 - (E6) No. 2:

   DTC P0204; (B134) No. 13 - (E17) No. 2:

   Is the resistance less than 1 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 fuel injector connector
   • Poor contact of coupling connector
4. CHECK FUEL INJECTOR  .

   Check the fuel injector on faulty cylinder. Ref. to FUEL INJECTION (FUEL SYSTEMS) (STI)>Fuel Injector>INSPECTION .

   Is the check result OK?

   Yes:  Go to  5

   No:  Replace the fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (STI)>Fuel Injector .

5. CHECK FOR POOR CONTACT  .

   Check for poor contact of ECM connector.

   Is there poor contact of ECM connector?

   Yes:  Repair the poor contact of ECM connector.

   No:  Go to  6

6. CHECK FUEL INJECTOR OPERATION  .
   1. Connect all connectors.
   2. Start the engine.
   3. Check if the corresponding fuel injector emits operating sound.
      NOTE: Use a sound scope to check the operating sound.

   Does the fuel injector emit operating sound?

   Yes:  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.

   No:  Repair the poor contact of fuel injector connector.