Inspection Procedure 31: Exhaust Gas Temperature Sensor System








OPERATION



  • A power voltage of 5 V is applied to the exhaust gas temperature sensor output terminal (terminal No. 1) from the engine-ECU (terminal No. 16).
  • The power voltage is earthed to the engine-ECU (terminal No. 8) from the exhaust gas temperature sensor (terminal No. 2).

FUNCTION



  • The 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 output voltage for DPF regeneration control.
  • The exhaust gas temperature sensor is a kind of resistor, which has characteristics to increase its resistance as the exhaust gas temperature rises. Therefore, the sensor output voltage varies with the exhaust gas temperature, and becomes upper as the exhaust gas temperature rises.

PROBABLE CAUSES



  • Failed exhaust gas temperature sensor
  • Open/short circuit or harness damage in exhaust gas temperature sensor circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

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

  • Refer to Data List Reference Table .

  1. Item 135: 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: C-133 exhaust gas temperature sensor connector

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

STEP 3. Check exhaust gas temperature sensor itself.

  • Check exhaust gas temperature sensor itself (Refer to GROUP 17 - Emission Control <4HN> - Diesel Particulate Filter (DPF) System - exhaust gas temperature sensor Check ).

Q. Is the check result normal?
Go to Step 4 .
Replace the exhaust gas temperature sensor.

STEP 4. Perform voltage measurement at C-133 exhaust gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal 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-18 engine-ECU connector.

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

STEP 6. Check harness between C-133 (terminal No. 1) exhaust gas temperature sensor connector and B-18 (terminal No. 16) engine-ECU connector.

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 135: 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 C-133 exhaust gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal No. 2 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-18 engine-ECU connector

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

STEP 10. Check harness between C-133 (terminal No. 2) exhaust gas temperature sensor connector and B-18 (terminal No. 8) 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-18 engine-ECU connector.

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

STEP 12. Check harness between C-133 (terminal No. 1) exhaust gas temperature sensor connector and B-18 (terminal No. 16) engine-ECU connector.

  • Check output line for damage.

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