SFI SYSTEM (for Sedan) > ECM Power Source Circuit


DESCRIPTION

When the ignition switch is turned to ON, the battery voltage is applied to the IGSW of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the integration relay (EFI relay) and supplying power to terminals +B and +B2 of the ECM.

WIRING DIAGRAM


A107913E03


INSPECTION PROCEDURE

1.INSPECT INTEGRATION NO.1 RELAY (POWER SOURCE OF INTEGRATION RELAY)


    A107914E01

  1. Remove the integration relay from the engine room relay block.

  1. Measure the voltage between the terminal of the integration relay and body ground.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    Engine room relay block
    (1C-1) - Body ground
    		11 to 14 V

  1. Reinstall the integration relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - INTEGRATION RELAY)
OK


2.INSPECT INTEGRATION NO.1 RELAY (EFI RELAY AND IG2 RELAY)
A107921E01

  1. Remove the integration relay from the engine room relay block.

  1. Inspect the EFI fuse and the AM2 fuse.

    1. Remove the EFI fuse and AM2 fuse from the integration relay.

    2. Check the resistance of the EFI fuse and AM2 fuse.

      Standard resistance:
      Below 1 Ω

    3. Reinstall the EFI fuse and the AM2 fuse.

  1. Inspect the EFI relay and the IG2 relay.

    1. Check the resistance between the terminals shown below.

      Standard resistance:
      Tester Connections
      		Specified Conditions
      1C-1 - 1A-4
      		10 kΩ or higher
      Below 1 Ω
      (when battery voltage is applied to terminals 1A-2 and 1A-3)
      1C-1 - 1B-4
      		10 kΩ or higher
      Below 1 Ω
      (when battery voltage is applied to terminals 1B-2 and 1B-3)
      1C-1 - 1B-1
      		Below 1 Ω

    2. Reinstall the integration relay.



NG
REPLACE INTEGRATION NO.1 RELAY
OK


3.CHECK HARNESS AND CONNECTOR (+B, +B2 AND MREL CIRCUIT)


    A107915E03

  1. Check the harness and the connectors between the integration relay and the ECM.

    1. Remove the integration relay from the engine room relay block.

    2. Disconnect the A21 ECM connector.

    3. Check the resistance.

      Standard resistance (Check for open):
      Tester Connections
      		Specified Conditions
      MREL (A21-44) - Engine room relay block (1A-2)
      		Below 1 Ω
      +B (A21-2) - Engine room relay block (1A-4)
      +B2 (A21-1) - Engine room relay block (1A-4)

      Standard resistance (Check for short):
      Tester Connections
      		Specified Conditions
      MREL (A21-44) or Engine room relay block (1A-2) - Body ground
      		10 kΩ or higher
      +B (A21-2) or Engine room relay block (1A-4) - Body ground
      +B2 (A21-1) or Engine room relay block (1A-4) - Body ground

  1. Check the harness and the connector between the integration relay and body ground.

    1. Check the resistance.

      Standard resistance (Check for open):
      Tester Connections
      		Specified Conditions
      Engine room relay block (1A-3) - Body ground
      		Below 1 Ω

  1. Reinstall the integration relay.

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4.CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND)


    A107892E01

  1. Disconnect the C20 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    E1 (C20-104) - Body ground
    		Below 1 Ω

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


5.INSPECT ECM (IGSW VOLTAGE)


    A107934E01

  1. Disconnect the C20 and A21 ECM connectors.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the terminals of the C20 and A21 ECM connectors.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    IGSW (A21-28) - E1 (C20-104)
    		11 to 14 V

  1. Reconnect the ECM connectors.



NG
Go to step 6
OK

REPLACE ECM (Click here)  

6.INSPECT FUSE (IGN FUSE)
A107935E06

  1. Remove the IGN fuse from the main body ECU.

  1. Check the IGN fuse resistance.

    Standard resistance:
    Below 1 Ω

  1. Reinstall the IGN fuse.



NG
CHECK FOR SHORTS IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE
OK


7.CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - ECM)
A107915E04

  1. Remove the integration relay from the engine room relay block.

  1. Disconnect the A21 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    Engine room relay block (1B-4) - IGSW (A21-28)
    		Below 1 Ω

    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    Engine room relay block (1B-4) or IGSW (A21-28) - Body ground
    		10 kΩ or higher

  1. Reinstall the integration relay.

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


8.CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - IGNITION SWITCH)
A107916E03

  1. Check the harness and the connectors between the integration relay and the ignition switch.

    1. Remove the integration relay from the engine room relay block.

    2. Disconnect the D8 ignition switch connector.

    3. Check the resistance.

      Standard resistance (Check for open):
      Tester Connections
      		Specified Conditions
      Engine room relay block (1B-2) - IG2 (D8-6)
      		Below 1 Ω

      Standard resistance (Check for short):
      Tester Connections
      		Specified Conditions
      Engine room relay block (1B-2) or IG2 (D8-6) - Body ground
      		10 kΩ or higher

  1. Check the harness and the connectors between the integration relay and body ground.

    1. Check the resistance.

      Standard resistance (Check for open):
      Tester Connections
      		Specified Conditions
      Engine room relay block (1B-3) - Body ground
      		Below 1 Ω

  1. Reinstall the integration relay.

  1. Reconnect the ignition switch connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


9.INSPECT IGNITION SWITCH
A107906E01

  1. Disconnect the D8 ignition switch connector.

  1. Check the resistance between the terminals shown below.

    Standard resistance:
    Tester Connections
    		Key Positions
    		Specified Conditions
    -
    		LOCK
    		10 kΩ or higher
    2-4
    		ACC
    		Below 1 Ω
    1-2-4
    		ON
    5-6
    1-3-4
    		START
    5-6-7

  1. Reconnect the ignition switch connector.



NG
REPLACE IGNITION SWITCH
OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (IGNITION SWITCH - INTEGRATION RELAY)