Code No. P0546: No. 1 exhaust gas temperature sensor Circuit High Input
OPERATION
- A power voltage of 5 V is applied to the No. 1 exhaust gas temperature sensor output terminal from the engine-ECU connector terminal DTS1.
- The power voltage is earthed to the engine-ECU connector terminal DT1E from the No. 1 exhaust gas temperature sensor connector terminal.
FUNCTION
- The No. 1 exhaust gas temperature sensor converts the exhaust gas temperature into a voltage and inputs the voltage signal to the engine-ECU.
- Engine-ECU uses this voltage for DPF regeneration control.
- The No. 1 exhaust gas temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the exhaust gas temperature rises. Therefore, the sensor output voltage varies with the exhaust gas temperature, and becomes lower as the exhaust gas temperature rises.
TROUBLE JUDGEMENT
Check Conditions
- Battery positive voltage is 8 - 16 V.
- 2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
- Vehicle speed is 20 km/h or higher.
Judgement Criterion
- The No. 1 exhaust gas temperature sensor output voltage is 4.95 V or more.
FAIL-SAFE AND BACKUP FUNCTION
- The throttle valve is opened (electrical discontinuity).
- The EGR control is stopped (fully closed).
- The DPF regeneration is prohibited.
PROBABLE CAUSES
- Failed No. 1 exhaust gas temperature sensor
- Open circuit or harness damage in No. 1 exhaust gas temperature sensor circuit or loose connector contact
- Failed engine-ECU
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STEP 1. M.U.T.-III data list
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- Refer to Data List Reference Table
- Item 117: No. 1 exhaust gas temperature sensor
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Q.
Is the check result normal?
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 Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
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 Go to Step 2.
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STEP 2. Check No. 1 exhaust gas temperature sensor itself.
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- Check No. 1 exhaust gas temperature sensor itself (Refer to GROUP 17 - Emission Control <DIESEL> - Diesel Particulate Filter (DPF) System - No. 1 exhaust gas temperature sensor Check ).
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Q.
Is the check result normal?
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Go to Step 3.
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Replace the No. 1 exhaust gas temperature sensor. After replacing the No. 1 exhaust gas temperature sensor, carry out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control <DIESEL> - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).
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STEP 3. Voltage measurement at No. 1 exhaust gas temperature sensor connector (DTS1 line).
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(1)Disconnect the connector, and measure at the wiring harness side.
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(3)Check the voltage between the No. 1 exhaust gas temperature sensor connector (DTS1 line) and body earth.
OK: 4.5 - 4.9 V
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Q.
Is the check result normal?
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Go to Step 6.
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Go to Step 4.
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STEP 4. Check of open circuit in DTS1 line between No. 1 exhaust gas temperature sensor connector and 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 connector(s) or wiring harness.
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STEP 5. M.U.T.-III data list
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- Refer to Data List Reference Table
- Item 117: No. 1 exhaust gas temperature sensor
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Q.
Is the check result normal?
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions).
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Replace the engine-ECU.
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STEP 6. Resistance measurement at No. 1 exhaust gas temperature sensor connector (DT1E line).
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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 No. 1 exhaust gas temperature sensor connector (DT1E line) and body earth.
OK: Continuity (2 Ω or less)
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Q.
Is the check result normal?
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Go to Step 8.
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Go to Step 7.
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STEP 7. Check of open circuit and damage in DT1E line between No. 1 exhaust gas temperature sensor connector and 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 connector(s) or wiring harness.
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STEP 8. Check of damage in DTS1 line between No. 1 exhaust gas temperature sensor connector and 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 connector(s) or wiring harness.
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