Inspection Procedure 3: Abnormality in KOS-ECU power supply and earth circuits.


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

PROBABLE CAUSES



DIAGNOSIS PROCEDURE


STEP 1. Resistance measurement at KOS-ECU connector (GND terminal)


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

Q. Is the check result normal?

Go to Step 3.

Go to Step 2.

STEP 2. Check of open circuit in GND line between KOS-ECU connector and body earth


Q. Is the check result normal?

Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

Repair the connector(s) or wiring harness.

STEP 3. Voltage measurement at KOS-ECU connector (IG1 terminal)


(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the voltage between the KOS-ECU connector (IG1 terminal) and body earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 5.

Go to Step 4.

STEP 4. Check of short to power supply, short to earth, and open circuit in IG1 line between ETACS-ECU connector and KOS-ECU connector


Q. Is the check result normal?

Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

Repair the connector(s) or wiring harness.

STEP 5. Voltage measurement at KOS-ECU connector (PWR terminal)


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

Q. Is the check result normal?

Replace the KOS-ECU and register the chassis number (Refer to ).

Go to Step 6.

STEP 6. Check of short to power supply, short to earth, and open circuit in PWR line between fusible link (4) and KOS-ECU connector


Q. Is the check result normal?

Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

Repair the connector(s) or wiring harness.