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Inspection Procedure 1: Abnormality in OSS-ECU power supply and ground circuit
 
 
cautionBefore 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 scan tool (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 Ω or less)
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of open circuit in PGND line between 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. 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 Ω or less)
Is the check result normal?
Go to Step 5.
Go to Step 4.
 
STEP 4. Check of open circuit in SGND line between 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 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: System voltage
Is the check result normal?
Go to Step 7.
Go to Step 6.
 
STEP 6. Check of short to power supply, short to ground, and open circuit in +B1 line between fusible link and 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.
 
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: System voltage
Is the check result normal?
Replace the OSS-ECU and register the VIN (Refer to ).
Go to Step 8.
 
STEP 8. Check of short to power supply, short to ground, and open circuit in +B2 line between fusible link and 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.