Inspection Procedure 1: Abnormality in OSS-ECU power supply and earth circuit


caution Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.

COMMENTS ON TROUBLE SYMPTOM



PROBABLE CAUSES



  • Damaged harness wires and connectors
  • Malfunction of OSS-ECU

DIAGNOSIS PROCEDURE


STEP 1. Resistance measurement at OSS-ECU connector (PGND terminal)


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the resistance between the OSS-ECU connector (PGND terminal) and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?





STEP 2. Check of open circuit in PGND line between OSS-ECU connector and earth joint connector


note Before the wiring harness check, check the joint connector, and repair if necessary.

Q. Is the check result normal?





STEP 3. Resistance measurement at OSS-ECU connector (SGND terminal)


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the resistance between the OSS-ECU connector (SGND terminal) and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?





STEP 4. Check of open circuit in SGND line between OSS-ECU connector and earth joint connector


Q. Is the check result normal?





STEP 5. Voltage measurement at OSS-ECU connector (+B1 terminal)


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the voltage between the OSS-ECU connector (+B1 terminal) and body earth.
OK: System voltage

Q. Is the check result normal?





STEP 6. Check of short to power supply, short to earth, and open circuit in +B1 line between fusible link and OSS-ECU connector


note Before the wiring harness check, check the ETACS-ECU connector and joint connector, and repair if necessary.

Q. Is the check result normal?





STEP 7. Voltage measurement at OSS-ECU connector (+B2 terminal)


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the voltage between the OSS-ECU connector (+B2 terminal) and body earth.
OK: System voltage

Q. Is the check result normal?





STEP 8. Check of short to power supply, short to earth, and open circuit in +B1 line between fusible link and OSS-ECU connector


note Before the wiring harness check, check the ETACS-ECU connector and joint connector, and repair if necessary.

Q. Is the check result normal?