SFI SYSTEM > ECM Power Source Circuit

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DESCRIPTION

When the ignition switch is turned to the ON position, the battery voltage is applied to terminal IGSW of the ECM. The ECM MREL output signal causes a current to flow to the coil, closing the contacts of the EFI relay and supplying power to terminal +B of the ECM.
If the ignition switch is turned off, the ECM holds the EFI relay ON for a maximum of 2 seconds to allow for the initial setting of the throttle valve.
When the ignition switch is turned to the ON position, voltage from the ECM's MREL terminal is applied to the engine room junction block (EFI relay). This causes the contacts of the engine room junction block (EFI relay) to close, which supplies power to terminal +B or +B2 of the ECM.

WIRING DIAGRAM


A138969E01


INSPECTION PROCEDURE

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


    A137016E02
  1. Disconnect the C58 (RHD) or C55 (LHD) ECM connector.

  1. Measure the resistance between the terminals.

    Standard resistance:
    RHD:
    Tester Connection
    Specified Condition
    E1 (C58-81) - Body ground
    Below 1 Ω
    LHD:
    Tester Connection
    Specified Condition
    E1 (C55-81) - Body ground
    Below 1 Ω
  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


2.CHECK ENGINE ROOM JUNCTION BLOCK (EFI RELAY VOLTAGE)


    A135182E02
  1. Remove the engine room junction block from the engine room R/B.

  1. Turn the ignition switch to the ON position.

  1. Measure the voltage between the terminals.

    Standard voltage:
    Tester Connection
    Specified Condition
    1E-6 - Body ground
    9 to 14 V


OK
Go to step 5
NG


3.INSPECT EFI MAIN FUSE


    A137020E01
  1. Remove the EFI MAIN fuse from the engine room R/B.

  1. Measure the EFI MAIN fuse resistance.

    Standard resistance:
    Below 1 Ω
  1. Reinstall the EFI MAIN fuse.



NG
REPLACE EFI MAIN FUSE
OK


Go to step 6

4.CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK - BATTERY)


    A140659E02
  1. Disconnect the negative battery terminal.

  1. Disconnect the positive battery terminal.

  1. Remove the engine room junction block from the engine room R/B.

  1. Measure the resistance between the terminals.

    Standard resistance:
    Check for open:
    Tester Connection
    Specified Condition
    1G-1 - Positive battery terminal
    Below 1 Ω
    Check for short:
    Tester Connection
    Specified Condition
    1G-1 or Positive battery terminal - Body ground
    10 kΩ or higher
  1. Reinstall the engine room junction block.

  1. Reconnect the positive battery terminal.

  1. Reconnect the negative battery terminal.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)  

5.INSPECT ENGINE ROOM JUNCTION BLOCK (EFI RELAY)


    A135182E02
  1. Remove the engine room junction block from the engine room R/B.

  1. Measure the resistance between the terminals.

    Standard resistance:
    Tester Connection
    Specified Condition
    1E-6 - 1E-12
    10 kΩ or higher
    1E-6 - 1E-12
    Below 1 Ω
    (Apply battery voltage between terminals 1E-9 and 1E-11)
  1. Reinstall the engine room junction block.



NG
REPLACE ENGINE ROOM JUNCTION BLOCK
OK


6.INSPECT EFI NO. 2 FUSE


    A135067E01
  1. Remove the EFI No. 2 fuse from the engine room R/B.

  1. Measure the EFI No. 2 fuse resistance.

    Standard resistance:
    Below 1 Ω
  1. Reinstall the EFI No. 2 fuse.



NG
REPLACE EFI NO. 2 FUSE
OK


7.CHECK HARNESS AND CONNECTOR (ECM - ENGINE ROOM JUNCTION BLOCK)


    A140660E02
  1. Disconnect the A24 (RHD) or A55 (LHD) ECM connector.

  1. Remove the engine room junction block from the engine room R/B.

  1. Measure the resistance between the terminals.

    Standard resistance (Check for open):
    RHD:
    Tester Connection
    Specified Condition
    1E-6 - +B (A24-2)
    Below 1 Ω
    1E-6 - +B2 (A24-1)
    Below 1 Ω
    LHD:
    Tester Connection
    Specified Condition
    1E-6 - +B (A55-2)
    Below 1 Ω
    1E-6 - +B2 (A55-1)
    Below 1 Ω

    Standard resistance (Check for open):
    RHD:
    Tester Connection
    Specified Condition
    1E-6 or +B (A24-2) - Body ground
    10 kΩ or higher
    1E-6 or +B2 (A24-1) - Body ground
    10 kΩ or higher
    LHD:
    Tester Connection
    Specified Condition
    1E-6 or +B (A55-2) - Body ground
    10 kΩ or higher
    1E-6 or +B2 (A55-1) - Body ground
    10 kΩ or higher
  1. Reinstall the engine room junction block.

  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


8.INSPECT ECM (IGSW VOLTAGE)


    A115671E42
  1. Disconnect the A24 (RHD) or A55 (LHD) ECM connector.

  1. Measure the voltage between the terminals.

    Standard voltage:
    RHD:
    Tester Connection
    Specified Condition
    IGSW (A24-28) - Body ground
    9 to 14 V
    LHD:
    Tester Connection
    Specified Condition
    IGSW (A55-28) - Body ground
    9 to 14 V
  1. Reconnect the ECM connector.



OK
Go to step 12
NG


9.INSPECT IGNITION RELAY NO. 2


    B016200E02
  1. Remove the IG2 relay from the engine room R/B.

  1. Measure the resistance between the terminals.

    Standard resistance:
    Tester Connection
    Specified Condition
    3 - 5
    10 kΩ or higher
    3 - 5
    Below 1 Ω
    (Apply battery voltage between terminals 1 and 2)
  1. Reinstall the IG2 relay.



NG
REPLACE IGNITION RELAY NO. 2
OK


10.CHECK HARNESS AND CONNECTOR (IG2 RELAY - BODY GROUND)


    A137039E01
  1. Remove the IG2 relay from the engine room R/B.

  1. Measure the resistance between the terminals.

    Standard resistance:
    Tester Connection
    Specified Condition
    IG2 relay terminal 2 - Body ground
    Below 1 Ω
  1. Reinstall the IG2 relay.

    Result:
    Result
    Proceed to
    OK
    A
    NG
    B


B
REPAIR OR REPLACE HARNESS OR CONNECTOR
A


11.INSPECT IGNITION SWITCH ASSEMBLY


    A056879E35
  1. Disconnect the E23 ignition switch connector.

  1. Measure the resistance between the terminals.

    Standard resistance:
    Tester Connection
    Ignition Switch Position
    Specified Condition
    All terminals
    LOCK
    10 kΩ or higher
    2 - 4
    ACC
    Below 1 Ω
    1 - 2 - 4, 5 - 6
    ON
    1 - 3 - 4, 5 - 6 - 7
    START
  1. Reconnect the ignition switch connector.



NG
REPLACE IGNITION SWITCH ASSEMBLY
OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - BATTERY) 

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


    A115671E43
  1. Disconnect the A24 (RHD) or A55 (LHD) ECM connector.

  1. Measure the resistance between the terminals.

    Standard resistance:
    RHD:
    Tester Connection
    Specified Condition
    MREL (A24-24) - Body ground
    Below 1 Ω
    LHD:
    Tester Connection
    Specified Condition
    MREL (A55-24) - Body ground
    Below 1 Ω
  1. Reconnect the ECM connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ECM (Click here)