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 (terminal No. 2) from the engine-ECU (terminal No. 58).
  • The power voltage is earthed to the engine-ECU (terminal No. 82) from the No. 1 exhaust gas temperature sensor (terminal No. 1).

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 JUDGMENT


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.
Judgment 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.
  • The AS&G control 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

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III data list

  • Refer to Data List Reference Table

  1. Item 117: No. 1 exhaust gas temperature sensor

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Go to Step 2 .

STEP 2. Connector check: B-104 No. 1 exhaust gas temperature sensor connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Check No. 1 exhaust gas temperature sensor itself.

  • 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 ).

Q. Is the check result normal?
Go to Step 4 .
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 - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration ).

STEP 4. Perform voltage measurement at B-104 No. 1 exhaust gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 2 and earth.
OK: 4.5 - 4.9 V

Q. Is the check result normal?
Go to Step 8 .
Go to Step 5 .

STEP 5. Connector check: B-09 engine-ECU connector.

Q. Is the check result normal?
Go to Step 6 .
Repair or replace the connector.

STEP 6. Check harness between B-104 (terminal No. 2) No. 1 exhaust gas temperature sensor connector and B-09 (terminal No. 58) engine-ECU connector.

  • Check output line for open circuit.

Q. Is the check result normal?
Go to Step 7 .
Repair the damaged harness wire.

STEP 7. M.U.T.-III data list

  • Refer to Data List Reference Table

  1. Item 117: No. 1 exhaust gas temperature sensor

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Replace the engine-ECU.

STEP 8. Perform resistance measurement at B-104 No. 1 exhaust gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal No. 1 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 11 .
Go to Step 9 .

STEP 9. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?
Go to Step 10 .
Repair or replace the connector.

STEP 10. Check harness between B-104 (terminal No. 1) No. 1 exhaust gas temperature sensor connector and B-09 (terminal No. 82) engine-ECU connector.

  • Check earthing line for open circuit and damage.

Q. Is the check result normal?
Go to Step 7 .
Repair the damaged harness wire.

STEP 11. Connector check: B-09 engine-ECU connector.

Q. Is the check result normal?
Go to Step 12 .
Repair or replace the connector.

STEP 12. Check harness between B-104 (terminal No. 2) No. 1 exhaust gas temperature sensor connector and B-09 (terminal No. 58) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 7 .
Repair the damaged harness wire.