Inspection Procedure 33: Proportional Oxygen Sensor System
OPERATION
- Power is supplied to the heater power terminal (terminal
No. 4) of the proportional oxygen sensor connector from the engine-ECU (terminal No. 63, terminal
No. 75 and terminal No. 87).
- The heater (terminal No. 3) of the proportional oxygen sensor connector is controlled
by the power transistor in the engine-ECU (terminal No. 146).
- The oxygen concentration signal is inputted to the engine-ECU (terminal No. 62)
from the proportional oxygen sensor output terminal (terminal No. 6).
- The power voltage is earthed to the engine-ECU (terminal No. 74) from the proportional
oxygen sensor (terminal No. 2).
- The pump current is inputted to the engine-ECU (terminal No. 61) from the proportional
oxygen sensor output terminal (terminal No. 1).
- The lambda value signal is inputted to the engine-ECU (terminal No. 73) from the proportional
oxygen sensor output terminal (terminal No. 5).
FUNCTION
- The proportional oxygen sensor is used to detect the
oxygen concentration in the exhaust gas.
- The engine-ECU calculates the quantity and start of extended injection based on
this output signal.
- Proportional oxygen sensor heater control the current applied to the proportional
oxygen sensor heater circuit in accordance with signals from the engine-ECU.
PROBABLE CAUSES
- Failed proportional oxygen sensor heater
- Open/short circuit or harness damage in proportional oxygen sensor circuit or loose connector
contact
- Failed engine-ECU
DIAGNOSIS PROCEDURE |
STEP 1. Connector check: B-15 proportional oxygen sensor connector |
Q.
Is the check result normal?
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Go to Step 2 . |
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Repair or replace the connector. |
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STEP 2. Perform voltage measurement at B-15 proportional oxygen sensor connector. |
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OK: System voltage |
Q.
Is the check result normal?
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Go to Step 6 . |
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Go to Step 3 . |
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STEP 3. Connector check: B-17 engine-ECU connector. |
Q.
Is the check result normal?
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Go to Step 4 . |
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Repair or replace the connector. |
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STEP 4. Check harness between B-15 (terminal No. 4) proportional oxygen sensor connector and B-17 (terminal No. 63, terminal No. 75 and terminal No. 87) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 5 . |
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Repair the damaged harness wire. |
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STEP 5. Check trouble symptoms. |
Q.
Does trouble symptom persist?
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Replace the engine-ECU. |
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Intermittent (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunctions ). |
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STEP 6. Connector check: B-17 engine-ECU connector |
Q.
Is the check result normal?
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Go to Step 7 . |
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Repair or replace the connector. |
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STEP 7. Check harness between B-15 (terminal No. 4) proportional oxygen sensor connector and B-17 (terminal No. 63, terminal No. 75 and terminal No. 87) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 8 . |
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Repair the damaged harness wire. |
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STEP 8. Check harness between B-15 (terminal No. 3) proportional oxygen sensor connector and B-16 (terminal No. 146) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 9 . |
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Repair the damaged harness wire. |
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STEP 9. Check harness between B-15 (terminal No. 2) proportional oxygen sensor connector and B-17 (terminal No. 74) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 10 . |
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Repair the damaged harness wire. |
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STEP 10. Check harness between B-15 (terminal No. 6) proportional oxygen sensor connector and B-17 (terminal No. 62) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 11 . |
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Repair the damaged harness wire. |
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STEP 11. Check harness between B-15 (terminal No. 5) proportional oxygen sensor connector and B-17 (terminal No. 73) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 12 . |
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Repair the damaged harness wire. |
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STEP 12. Check harness between B-15 (terminal No. 1) proportional oxygen sensor connector and B-17 (terminal No. 61) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 13 . |
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Repair the damaged harness wire. |
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STEP 13. Replace the proportional oxygen sensor. |
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Q.
Does trouble symptom persist?
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Replace the engine-ECU. |
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The check is end. |
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