Inspection Procedure 3: Abnormality in KOS&OSS-ECU power supply and earth circuits.
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Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
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COMMENTS ON TROUBLE SYMPTOM
When the KOS does not work at all or the KOS&OSS-ECU cannot communicate with the M.U.T.-III, the power supply or earth circuit system of KOS&OSS-ECU may be faulty.
PROBABLE CAUSES
- Damaged wiring harness and connectors
- Malfunction of KOS&OSS-ECU
DIAGNOSIS PROCEDURE
STEP 1. Resistance measurement at KOS&OSS-ECU connector (PGND, SGND terminal)
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Measure the resistance between the KOS&OSS-ECU connector (PGND, SGND terminal) and body earth.
OK: Continuity exists (2 Ω or less)
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Q.
Is the check result normal?
Go to Step 3.
Go to Step 2.
STEP 2. Check of open circuit in PGND, SGND line between KOS&OSS-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 
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Repair the connector(s) or wiring harness.
STEP 3. Voltage measurement at KOS&OSS-ECU connector (+B, IOD terminal)
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(1)Disconnect the connector, and measure at the wiring harness side.
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(2)Check the voltage between the KOS&OSS-ECU connector (+B, IOD terminal) and body earth.
OK: System voltage
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Q.
Is the check result normal?
Replace the KOS&OSS-ECU and register the chassis number (Refer to ).
Go to Step 4.
STEP 4. Check of short to power supply, short to earth, and open circuit in +B, IOD line between fuse and KOS&OSS-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.