Code No. P0112: EGR Gas Temperature Sensor Circuit Low Input


OPERATION



  • A power voltage of 5 V is applied to the EGR gas temperature sensor output terminal from the engine-ECU connector terminal ETS.
  • The power voltage is earthed to the engine-ECU connector terminal ETSE from the EGR gas temperature sensor connector terminal.

FUNCTION



  • The EGR gas temperature sensor converts the EGR gas temperature into a voltage and inputs the voltage signal to the engine-ECU.
  • The EGR gas temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the EGR gas temperature rises. Therefore, the sensor output voltage varies with the EGR gas temperature, and becomes lower as the EGR 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.
Judgment Criterion
  • The EGR gas temperature sensor output voltage is 0.09 V or less.

FAIL-SAFE AND BACKUP FUNCTION



  • The intake air temperature is controlled to be 50°C.
  • The EGR control is stopped (fully closed).
  • The AS&G control is prohibited.

PROBABLE CAUSES



  • Failed EGR gas temperature sensor
  • Short circuit in EGR 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 8: EGR 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. Check EGR gas temperature sensor itself.

  • EGR gas temperature sensor connector check.
  • Check EGR gas temperature sensor itself (Refer to GROUP 17 - Emission Control <DIESEL> - Exhaust Gas Recirculation (EGR) System - EGR Gas Temperature Sensor Check ).

Q. Is the check result normal?
Go to Step 3.
Repair or replace the connector, or replace the EGR gas temperature sensor.

STEP 3. Perform voltage measurement at EGR gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal engine-ECU ETS line and body earth.
OK: 4.5 - 4.9 V

Q. Is the check result normal?
Go to Step 6.
Go to Step 4.

STEP 4. Check harness between EGR gas temperature sensor connector terminal and engine-ECU connector terminal ETS.

  • Check output line for short circuit.

Q. Is the check result normal?
Go to Step 5.
Repair or replace the connector, or repair the damaged harness wire.

STEP 5. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 8: EGR 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 6. Perform resistance measurement at EGR gas temperature sensor connector.

  • Disconnect connector, and measure at harness side.
  • Resistance between terminal engine-ECU ETSE line and body earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?
Go to Step 8.
Go to Step 7.

STEP 7. Check harness between EGR gas temperature sensor connector terminal and engine-ECU connector terminal ETSE.

  • Check earthing line for damage.

Q. Is the check result normal?
Go to Step 5.
Repair or replace the connector, or repair the damaged harness wire.

STEP 8. Check harness between EGR gas temperature sensor connector terminal and engine-ECU connector terminal ETS.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 5.
Repair or replace the connector, or repair the damaged harness wire.