Inspection Procedure 1

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

CAUTION:
Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.

TECHNICAL DESCRIPTION (COMMENT)

When OSS-ECU cannot communicate with the M.U.T.-III, the power supply or ground circuit system of OSS-ECU may be faulty.

TROUBLESHOOTING HINTS

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

DIAGNOSIS

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 ground.
OK: Continuity exists (2 ohm or less)


Q. Is the check result normal?

YES Go to Step 3.

NO Go to Step 2.

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

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

Q. Is the check result normal?

YES Intermittent malfunction is suspected How to Cope With Intermittent Malfunctions).

NO Repair the connector(s) or wiring harness.

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 ground.
OK: Continuity exists (2 ohm or less)


Q. Is the check result normal?

YES Go to Step 5.

NO Go to Step 4.

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

Q. Is the check result normal?

YES Intermittent malfunction is suspected How to Cope With Intermittent Malfunctions).

NO Repair the connector(s) or wiring harness.

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 ground.
OK: Battery voltage


Q. Is the check result normal?

YES Go to Step 7.

NO Go to Step 6.

STEP 6. Check of short to power supply, short to ground, and open circuit in +B1 line between fusible link (36) 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?

YES Intermittent malfunction is suspected How to Cope With Intermittent Malfunctions).

NO Repair the connector(s) or wiring harness.

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 ground.
OK: Battery voltage


Q. Is the check result normal?

YES Replace the OSS-ECU and register the VIN (Refer to Programming and Relearning).

NO Go to Step 8.

STEP 8. Check of short to power supply, short to ground, and open circuit in +B2 line between fusible link (34) 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?

YES Intermittent malfunction is suspected How to Cope With Intermittent Malfunctions).

NO Repair the connector(s) or wiring harness.