Inspection Procedure
1: Abnormality in OSS-ECU power supply and earth circuit
caution |
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 OSS-ECU cannot communicate with the M.U.T.-III, the power supply or earth circuit
system of OSS-ECU may be faulty.
PROBABLE CAUSES
- Damaged harness wires and connectors
- Malfunction of OSS-ECU
DIAGNOSIS PROCEDURE
STEP 1. Resistance measurement at OSS-ECU connector (PGND
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 OSS-ECU connector (PGND 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 line between OSS-ECU connector
and earth joint connector
note |
Before the wiring harness check, check the joint connector, and repair if necessary.
|
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. Resistance measurement at OSS-ECU connector (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 OSS-ECU connector (SGND terminal) and body earth. OK: Continuity exists (2 Ω or less)
|
Q.
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 earth joint 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 OSS-ECU connector (+B1 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 OSS-ECU connector (+B1 terminal) and body
earth. OK: System voltage
|
Q.
Is the check result normal?
Go to Step 7.
Go to Step 6.
STEP 6. Check of short to power supply, short to earth, and open circuit
in +B1 line between fusible link and OSS-ECU connector
note |
Before the wiring harness check, check the ETACS-ECU connector and joint connector, and repair
if necessary.
|
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 7. Voltage measurement at OSS-ECU connector (+B2 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 OSS-ECU connector (+B2 terminal) and body
earth. OK: System voltage
|
Q.
Is the check result normal?
Replace the OSS-ECU and register the chassis number (Refer to
).
Go to Step 8.
STEP 8. Check of short to power supply, short to earth, and open circuit
in +B1 line between fusible link and OSS-ECU connector
note |
Before the wiring harness check, check the ETACS-ECU connector and joint connector, and repair
if necessary.
|
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.