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 .

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-32 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-32 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-51 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-51 engine-ECU connector

Q. Is the check result normal?

	Go to Step 6 .

	Repair or replace the connector.

STEP 6. Check harness between B-32 (terminal No. 3) EGR valve assembly connector and B-51 (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 .

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-51 engine-ECU connector.

Q. Is the check result normal?

	Check and repair harness between B-32 (terminal No. 3) EGR valve assembly connector and B-51 (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-32 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-51 engine-ECU connector

Q. Is the check result normal?

	Go to Step 11 .

	Repair or replace the connector.

STEP 11. Check harness between B-32 (terminal No. 2) EGR valve assembly connector and B-51 (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-32 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-51 engine-ECU connector

Q. Is the check result normal?

	Go to Step 14 .

	Repair or replace the connector.

STEP 14. Check harness between B-32 (terminal No. 1) EGR valve assembly connector and B-51 (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-51 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-51 engine-ECU connector

Q. Is the check result normal?

	Check and repair check harness between B-32 (terminal No. 1) EGR valve assembly connector and B-51 (terminal No. 57) engine-ECU connector. Check output line for open circuit and damage.

	Repair or replace the connector.

STEP 17. Connector check: B-51 engine-ECU connector

Q. Is the check result normal?

	Go to Step 7 .

	Repair or replace the connector.