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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.-IIISE), 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
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
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 ground joint connector
noteBefore the wiring harness check, check the joint connector, and repair if necessary.
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 ground joint 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 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
noteBefore the wiring harness check, check the ETACS-ECU connector and joint connector, and repair if necessary.
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 +B1 line between fusible link and OSS-ECU connector
noteBefore the wiring harness check, check the ETACS-ECU connector and joint connector, and repair if necessary.
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.