DTC P0351: Ignition Coil "A" Primary Control Circuit/Open: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

• Improper idling
• Poor driving performance
  CAUTION:

  • After servicing or replacing faulty parts, perform Clear Memory Mode Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>CLEAR MEMORY MODE>OPERATION , and inspection mode Refer 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 Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK IGNITION COIL POWER SUPPLY CIRCUIT. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ignition coil.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between ignition coil connector and engine ground.

      Connector & terminal 

      DTC P0351; (E31) No. 1 (+) - Engine ground (-):

      DTC P0352; (E32) No. 1 (+) - Engine ground (-):

      DTC P0353; (E33) No. 1 (+) - Engine ground (-):

      DTC P0354; (E34) 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 or short to ground in harness of power supply circuit
   • Blown out of fuse
   • Poor contact of IG relay connector
   • Poor contact of coupling connector
   • Faulty IG relay
2. CHECK HARNESS OF IGNITION COIL GROUND CIRCUIT. 
   1. Turn the ignition switch to OFF.
   2. Measure the resistance of harness between ignition coil connector and engine ground.

      Connector & terminal 

      DTC P0351; (E31) No. 3 - Engine ground:

      DTC P0352; (E32) No. 3 - Engine ground:

      DTC P0353; (E33) No. 3 - Engine ground:

      DTC P0354; (E34) No. 3 - Engine ground:

   Is the resistance less than 5 Ω?

   Yes:  Go to  3.

   No:  Repair the open circuit in harness between ignition coil connector and engine grounding terminal.

3. CHECK HARNESS BETWEEN ECM AND IGNITION COIL CONNECTOR. 
   1. Disconnect the connector from ECM.
   2. Measure the resistance between ignition coil connector and engine ground.

      Connector & terminal 

      DTC P0351; (E31) No. 2 - Engine ground:

      DTC P0352; (E32) No. 2 - Engine ground:

      DTC P0353; (E33) No. 2 - Engine ground:

      DTC P0354; (E34) No. 2 - Engine ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  4.

   No:  Repair the ground short circuit of harness between ECM connector and ignition coil connector.

4. CHECK HARNESS BETWEEN ECM AND IGNITION COIL CONNECTOR. 

   Measure the resistance of harness between ECM connector and ignition coil connector.

   Connector & terminal 

   DTC P0351; (E159) No. 8 - (E31) No. 2:

   DTC P0352; (E159) No. 16 - (E32) No. 2:

   DTC P0353; (E159) No. 24 - (E33) No. 2:

   DTC P0354; (E159) No. 32 - (E34) No. 2:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair the open circuit in harness between ECM connector and ignition coil connector.

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 SPARK PLUG CONDITION. 
   1. Remove the spark plug of the corresponding cylinder. Refer to IGNITION (EXCEPT FOR STI)>SPARK PLUG>REMOVAL .
   2. Check the spark plug condition. Refer to IGNITION (EXCEPT FOR STI)>SPARK PLUG>INSPECTION .

   Is the check result OK?

   Yes:  Replace the ignition coil. Refer to IGNITION (EXCEPT FOR STI)>IGNITION COIL .

   No:  Replace the spark plug. Refer to IGNITION (EXCEPT FOR STI)>SPARK PLUG .