Inspection Procedure 36: Engine-ECU or Engine-A-M/T-ECU Power Supply, Engine Control Relay, Ignition Switch-IG1 System




OPERATION



FUNCTION



PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. Check battery voltage.

  • Measure battery voltage during cranking.
OK: 8 V or more

Q. Is the check result normal?
Go to Step 2 .
Check battery (Refer to GROUP 54A - Battery - On-vehicle Service - Battery test ).

STEP 2. Connector check: B-206 engine control relay connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace the connector.

STEP 3. Check engine control relay.

  • Check engine control relay (Refer to ).

Q. Is the check result normal?
Go to Step 4 .
Replace the engine control relay.

STEP 4. Perform voltage measurement at B-206 engine control relay connector.


  • Remove relay, and measure at J/B side.
  • Voltage between terminal No. 1 and earth, also between terminal No. 3 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 5 .


    Check intermediate connector B-208, and repair if necessary. If intermediate connector is normal, check and repair harness between B-206 (terminal No. 1 and terminal No. 3) engine control relay connector and battery.

    • Check power supply line for open/short circuit.

STEP 5. Connector check: A-09 engine-ECU connector or engine-A-M/T-ECU connector.

Q. Is the check result normal?

Go to Step 6 .

Repair or replace the connector.

STEP 6. Perform voltage measurement at A-09 engine-ECU connector or engine-A-M/T-ECU connector.


  • Disconnect engine-ECU connector or engine-A-M/T-ECU connector, and connect special tool power plant ECU check harness (MB991987), and then measure the voltage on the check connector.
  • Ignition switch: ON
  • Voltage between terminal No. 77 and earth also between terminal No. 92 and earth.
OK: System voltage

Q. Is the check result normal?


    Check intermediate connector B-212, and repair if necessary. If intermediate connector is normal, check and repair harness between B-206 (terminal N0. 2) engine control relay connector nd A-09 (terminal No. 107) engine-ECU connector or engine-A-M/T-ECU connector.

    • Check earthing line for short circuit.

Go to Step 7 .

STEP 7. Check harness between B-206 engine control relay connector and A-09 engine-ECU connector or engine-A-M/T-ECU connector.



  1. Check and repair harness between B-206 (terminal No. 4) engine control relay connector and A-09 (terminal No. 77) engine-ECU connector or engine-A-M/T-ECU connector.
  2. Check and repair harness between B-206 (terminal No. 4) engine control relay connector and A-09 (terminal No. 92) engine-ECU connector or engine-A-M/T-ECU connector.

  • Check power supply line for open/short circuit damage.

Q. Is the check result normal?

Go to Step 8 .

Repair the damaged harness wire.

STEP 8. Check harness between B-206 (terminal No. 2) engine control relay connector and A-09 (terminal No. 107) engine-ECU connector or engine-A-M/T-ECU connector.


note Before checking harness, check intermediate connectors B-210 and B-229 and repair if necessary.

  • Check output line for open circuit and damage.

Q. Is the check result normal?

Go to Step 9 .

Repair the damaged harness wire.

STEP 9. Perform voltage measurement at A-09 engine-ECU connector or engine-A-M/T-ECU connector.


  • Disconnect connector and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 122 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 12 .

Go to Step 10 .

STEP 10. Connector check: B-240 ignition switch connector

Q. Is the check result normal?

Go to Step 11 .

Repair or replace the connector.

STEP 11. Check ignition switch.



  • Check ignition switch (Refer to GROUP 54A - Ignition Switch - Inspection ).

Q. Is the check result normal?


    Check intermediate connectors B-210 and B-229, and repair if necessary. If intermediate connectors are normal, check and repair harness between B-240 (terminal No. 2) ignition switch connector and A-09 (terminal No. 122) engine-ECU connector or engine-A-M/T-ECU connector.

    • Check output line for open/short circuit.

Replace the ignition switch.

STEP 12. Check harness between B-206 (terminal No. 1 and terminal No. 3) engine control relay connector and battery.

note Before checking harness, check intermediate connector B-208, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?

Go to Step 13 .

Repair the damaged harness wire.

STEP 13. Check harness between B-240 (terminal No. 2) ignition switch connector and A-09 (terminal No. 122) engine-ECU connector or engine-A-M/T-ECU connector.


note Before checking harness, check intermediate connectors B-210 and B-229 and repair necessary.

  • Check output line for damage.

Q. Is the check result normal?

Go to Step 14 .

Repair the damaged harness wire.

STEP 14. Check harness between A-09 engine-ECU connector or engine-A-M/T-ECU connector and body earth.


  1. Check and repair harness between A-09 (terminal N0. 75) engine-ECU connector or engine-A-M/T-ECU connector and body earth.
  2. Check and repair harness between A-09 (terminal No. 76) engine-ECU connector or engine-A-M/T-ECU connector and body earth.
note Before checking harness, check intermediate connector A-14, and repair if necessary.

  • Check earthing line for open circuit damage.

Q. Is the check result normal?

Replace the engine-ECU or engine-A-M/T-ECU then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).

Repair the damaged harness wire.