Ignition Control System: Wiring Diagram

Fig 1: Identifying Ignition Control System Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE FOR SYMPTOM

Step	Check	Yes	No
1 CHECK SPARK PLUG CONDITION. Remove the spark plug. <Ref. to REMOVAL , Spark Plug.> Check the spark plug condition. <Ref. to INSPECTION , Spark Plug.>	Is the spark plug condition normal?	Go to step 2 .	Replace the spark plug. <Ref. to REMOVAL , Spark Plug.>
2 CHECK IGNITION SYSTEM FOR SPARKS. Connect the spark plug to ignition coil. Release the fuel pressure. <Ref. to PROCEDURE , Fuel.> Contact the spark plug thread portion to engine. While opening the throttle valve fully, start the engine to check if spark occurs at each cylinder.	Does spark occur at each cylinder?	Check fuel pump system. <Ref. to FUEL PUMP CIRCUIT , Diagnostics for Engine Starting Failure.>	Go to step 3 .
3 CHECK POWER SUPPLY CIRCUIT FOR IGNITION COIL. Turn the ignition switch to OFF. Disconnect the connector from ignition coil. Turn the ignition switch to ON. Measure the power supply voltage between ignition coil connector and engine ground. Connector & terminal (E31) No. 3 (+) - Engine ground (-): (E32) No. 3 (+) - Engine ground (-): (E33) No. 3 (+) - Engine ground (-): (E34) No. 3 (+) - Engine ground (-): (E45) No. 3 (+) - Engine ground (-): (E46) No. 3 (+) - Engine ground (-):	Is the voltage 10 V or more?	Go to step 4 .	Repair the harness and connector. NOTE: In this case, repair the following item: Open circuit of harness between ignition coil and oxygen sensor relay connector Poor contact of coupling connector
4 CHECK HARNESS OF IGNITION COIL GROUND CIRCUIT. Turn the ignition switch to OFF. Measure the resistance between ignition coil connector and engine ground. Connector & terminal (E31) No. 2 - Engine ground: (E32) No. 2 - Engine ground: (E33) No. 2 - Engine ground: (E34) No. 2 - Engine ground: (E45) No. 2 - Engine ground: (E46) No. 2 - Engine ground:	Is the resistance less than 5 Ω?	Go to step 5 .	Repair the harness and connector. NOTE: In this case, repair the following item: Open circuit of harness between the ignition coil connector and ECM connector Open circuit of harness between ECM and engine ground terminal Poor contact of coupling connector
5 CHECK HARNESS BETWEEN ECM AND IGNITION COIL CONNECTOR. Turn the ignition switch to OFF. Disconnect connectors from the ECM. Disconnect the connector from ignition coil. Measure the resistance of harness between the ECM and ignition coil connector. Connector & terminal (B137) No. 18 - (E31) No. 1: (B137) No. 19 - (E32) No. 1: (B137) No. 20 - (E33) No. 1: (B137) No. 21 - (E34) No. 1: (B137) No. 22 - (E45) No. 1: (B137) No. 23 - (E46) No. 1:	Is the resistance less than 1 Ω?	Go to step 6 .	Repair the harness and connector. NOTE: In this case, repair the following item: Open circuit of harness between the ECM and ignition coil connector Poor contact of coupling connector
6 CHECK HARNESS BETWEEN ECM AND IGNITION COIL CONNECTOR. Measure the resistance of harness between ECM and engine ground. Connector & terminal: (B137) No. 18 - Engine ground: (B137) No. 19 - Engine ground: (B137) No. 20 - Engine ground: (B137) No. 21 - Engine ground: (B137) No. 22 - Engine ground: (B137) No. 23 - Engine ground:	Is the resistance 1 MΩ or more?	Go to step 7 .	Repair the ground short circuit of harness between the ECM and ignition coil connector.
7 CHECK POOR CONTACT. Check for poor contact of the ECM connector.	Is there poor contact in ECM connector?	Repair poor contact of the ECM connector.	Replace the ignition coil. <Ref. to SPARK PLUG .>