Code No. P0489: EGR Valve Position Sensor Circuit Low Input


OPERATION



  • A power voltage of 5 V is applied to the EGR valve assembly power terminal (terminal No. 3) from the engine-ECU (terminal No. 71) and earthed to the engine-ECU (terminal No. 81) from the EGR valve assembly (terminal No. 2).
  • The sensor signal is inputted to the engine-ECU (terminal No. 57) from the EGR valve assembly output terminal (terminal No. 1).

FUNCTION



  • The EGR valve assembly detects the position of the EGR valve and sends the signal to the engine-ECU.
  • Based on the signal, the engine-ECU performs the feedback control of the EGR valve.

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 valve position sensor output voltage is 0.20 V or less.

FAIL-SAFE AND BACKUP FUNCTION



  • The DPF regeneration is prohibited.
  • The throttle valve is opened (Electrical discontinuity).
  • The EGR control is stopped (fully closed).
  • The AS&G control is prohibited.

PROBABLE CAUSES



  • Failed EGR valve position sensor
  • Open/short circuit or harness damage in EGR valve position 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 16: EGR valve position 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-16 EGR valve assembly connector

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

STEP 3. Perform voltage measurement at B-16 EGR valve assembly connector.

  • Use special tool test harness(MB991658) to connect connector and measure at pick-up harness.
  • Ignition switch: ON
  • Voltage between terminal No. 3 and earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?
Go to Step 9 .
Go to Step 4 .

STEP 4. Perform voltage measurement at B-09 engine-ECU connector.

  • Disconnect engine-ECU harness, and connect special tool power plant ECU check harness (MB992291) to measure at connector for inspection.
  • Ignition switch: ON
  • Voltage between terminal No. 71 and earth.
OK: 4.9 - 5.1 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-16 (terminal No. 3) EGR valve assembly connector and B-09 (terminal No. 71) engine-ECU connector.

  • Check power supply line for short 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 16: EGR valve position 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. Connector check: B-09 engine-ECU connector.

Q. Is the check result normal?

    Check and repair harness between B-16 (terminal No. 3) EGR valve assembly connector and B-09 (terminal No. 71) engine-ECU connector.

    • Check power supply line for open circuit and damage.
Repair or replace the connector.

STEP 9. Perform resistance measurement at B-16 EGR valve assembly connector.

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

Q. Is the check result normal?
Go to Step 12 .
Go to Step 10 .

STEP 10. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?
Go to Step 11 .
Repair or replace the connector.

STEP 11. Check harness between B-16 (terminal No. 2) EGR valve assembly connector and B-09 (terminal No. 81) engine-ECU connector.

  • Check earthing line for damage.

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

STEP 12. Perform voltage measurement at B-16 EGR valve assembly connector.

  • Use special tool test harness (MB991658) to connect connector and measure at pick-up harness.
  • Engine: Idling (after warming up)
  • Voltage between terminal No. 1 and earth.
OK: 2.0 V or higher

Q. Is the check result normal?
Go to Step 15 .
Go to Step 13 .

STEP 13. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?
Go to Step 14 .
Repair or replace the connector.

STEP 14. Check harness between B-16 (terminal No. 1) EGR valve assembly connector and B-09 (terminal No. 57) engine-ECU connector.

  • Check output line for short circuit.

Q. Is the check result normal?
Replace the EGR valve assembly.
Repair the damaged harness wire.

STEP 15. Perform voltage measurement at B-09 engine-ECU connector.

  • Disconnect engine-ECU harness, and connect special tool power plant ECU check harness (MB992291) to measure at connector for inspection.
  • Engine: Idling (after warming up)
  • Voltage between terminal No. 57 and earth.
OK: 2.0 V or higher

Q. Is the check result normal?
Go to Step 17 .
Go to Step 16 .

STEP 16. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?

    Check and repair check harness between B-16 (terminal No. 1) EGR valve assembly connector and B-09 (terminal No. 57) engine-ECU connector.

    • Check output line for open circuit and damage.
Repair or replace the connector.

STEP 17. Connector check: B-09 engine-ECU connector

Q. Is the check result normal?
Go to Step 7 .
Repair or replace the connector.