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 from the engine-ECU connector terminal EGR5 and earthed to the engine-ECU connector terminal EGRE from the EGR valve assembly connector terminal.
  • The sensor signal is inputted to the engine-ECU connector terminal EGRP from the EGR valve assembly output terminal.

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. Perform voltage measurement at 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 engine-ECU EGR5 line and body earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?
Go to Step 6.
Go to Step 3.

STEP 3. Perform voltage measurement at 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 EGR5 and body earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?

    Repair or replace the connector, or check and repair harness between EGR valve assembly connector terminal and engine-ECU connector terminal EGR5.

    • Check power supply line for open circuit and damage.
Go to Step 4.

STEP 4. Check harness between EGR valve assembly connector terminal and engine-ECU connector terminal EGR5.

  • Check power supply 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 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 6. Perform resistance measurement at EGR valve assembly connector.

  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Resistance between terminal engine-ECU EGRE 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 valve assembly connector terminal and engine-ECU connector terminal EGRE.

  • 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. Perform voltage measurement at 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 engine-ECU EGRP line and body earth.
OK: 2.0 V or higher

Q. Is the check result normal?
Go to Step 10.
Go to Step 9.

STEP 9. Check harness between EGR valve assembly connector terminal and engine-ECU connector terminal EGRP.

  • Check output line for short circuit.

Q. Is the check result normal?
Replace the EGR valve assembly.
Repair or replace the connector, or repair the damaged harness wire.

STEP 10. Perform voltage measurement at 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 EGRP and body earth.
OK: 2.0 V or higher

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

    Repair or replace the connector, or check and repair check harness between EGR valve assembly connector terminal and engine-ECU connector terminal EGRP.

    • Check output line for open circuit and damage.