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Inspection Procedure 3: Abnormality in KOS&OSS-ECU power supply and ground circuits.
 
 
cautionBefore replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
 
 
 
 
COMMENTS ON TROUBLE SYMPTOM
When the KOS does not work at all or the KOS&OSS-ECU cannot communicate with the scan tool (M.U.T.-IIISE), the power supply or ground circuit system of KOS&OSS-ECU may be faulty.
 
 
PROBABLE CAUSES
  • Damaged wiring harness and connectors
  • Malfunction of KOS&OSS-ECU
 
 
DIAGNOSIS
STEP 1. Resistance measurement at KOS&OSS-ECU connector (PGND, SGND terminals)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between the KOS&OSS-ECU connector (PGND, SGND terminals) and body ground.
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of open circuit in PGND, SGND lines between KOS&OSS-ECU connector and body ground.
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&OSS-ECU connector (+B, IOD terminals)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Check the voltage between the KOS&OSS-ECU connector (+B, IOD terminals) and body ground.
OK: The voltage should measure approximately 12 volts (battery positive voltage).
Is the check result normal?
Replace the KOS&OSS-ECU and register the ID codes (Refer to ).
Go to Step 4.
 
STEP 4. Check of short to power supply, short to ground, and open circuit in +B, IOD line between fuse and KOS&OSS-ECU connector.
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.