Code No. P0489: Exhaust gas recirculation valve (stepper motor) circuit malfunction (Ground short) <Except vehicles for Russia>










OPERATION



  • Power is supplied to the exhaust gas recirculation valve (terminal No. 2 and No. 5) from the engine control relay (terminal No. 2).
  • The engine-ECU (terminal No. 31, No. 32, No. 47 and No. 48) makes the power transistor in the unit be in ON position, and that makes currents go on the exhaust gas recirculation valve (terminal No. 1, No. 3, No. 4 and No. 6).

FUNCTION



  • In response to the signal from the engine-ECU, the exhaust gas recirculation valve (stepper motor) controls a flow rate of exhaust gas recirculation.

TROUBLE JUDGMENT


Check Conditions
  • Ignition switch is "ON" position.
  • Battery positive voltage is 10 - 16.5 V.
Judgement Criterion
  • When the exhaust gas recirculation valve is de-energized, the engine-ECU voltage should be 1.5 V or less for 1.4 seconds.

PROBABLE CAUSES



  • Failed exhaust gas recirculation valve (stepper motor)
  • Open/short circuit or harness damage in exhaust gas recirculation valve (stepper motor) circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-32 exhaust gas recirculation valve connector

Q. Is the check result normal?
Go to Step 2 .
Repair or replace the connector.

STEP 2. Perform resistance measurement at B-32 exhaust gas recirculation valve connector.

  • Disconnect connector and measure at exhaust gas recirculation valve side.
  • Resistance between terminal No. 1 and No. 2.
  • Resistance between terminal No. 2 and No. 3.
  • Resistance between terminal No. 4 and No. 5.
  • Resistance between terminal No. 5 and No. 6.
OK: 20 - 24 Ω (at 20°C)

Q. Are the check results normal?
Go to Step 3 .
Replace the exhaust gas recirculation valve.

STEP 3. Perform voltage measurement at B-32 exhaust gas recirculation valve connector.

  • Disconnect connector and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal No. 2, No. 5 and earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 5 .
Go to Step 4 .

STEP 4. Connector check: A-33X engine control relay connector

Q. Is the check result normal?

    Check intermediate connector A-13, and repair if necessary. If intermediate connector is normal, check and repair harness between B-32 (terminal No. 2 and No. 5) exhaust gas recirculation valve connector and A-33X (terminal No. 2) engine control relay connector.

    • Check power supply line for open/short circuit.
Repair or replace the connector.

STEP 5. Perform voltage measurement at B-29 engine-ECU connector.

  • Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
  • Ignition switch: OFF → ON
  • Voltage between terminal No. 31, No. 32, No. 47, No. 48 and earth.
OK: To initialize, energize exhaust gas recirculation valve for three seconds and de-energize it.

Q. Is the check result normal?
Go to Step 9 .
Go to Step 6 .

STEP 6. Connector check: B-29 engine-ECU connector

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

STEP 7. Check harness between exhaust gas recirculation valve connector and engine-ECU connector.

  1. Check harness between B-32 (terminal No. 1) exhaust gas recirculation valve connector and B-29 (terminal No. 31) engine-ECU connector.
  2. Check harness between B-32 (terminal No. 3) exhaust gas recirculation valve connector and B-29 (terminal No. 32) engine-ECU connector.
  3. Check harness between B-32 (terminal No. 4) exhaust gas recirculation valve connector and B-29 (terminal No. 47) engine-ECU connector.
  4. Check harness between B-32 (terminal No. 6) exhaust gas recirculation valve connector and B-29 (terminal No. 48) engine-ECU connector.

  • Check output line for open/short circuit.

Q. Are the check results normal?
Go to Step 8 .
Repair the damaged harness wire.

STEP 8. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.

Q. Is diagnosis code set?
Replace the engine-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 9. Connector check: B-29 engine-ECU connector

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

STEP 10. Check harness between exhaust gas recirculation valve connector and engine-ECU connector.

  1. Check harness between B-32 (terminal No. 1) exhaust gas recirculation valve connector and B-29 (terminal No. 31) engine-ECU connector.
  2. Check harness between B-32 (terminal No. 3) exhaust gas recirculation valve connector and B-29 (terminal No. 32) engine-ECU connector.
  3. Check harness between B-32 (terminal No. 4) exhaust gas recirculation valve connector and B-29 (terminal No. 47) engine-ECU connector.
  4. Check harness between B-32 (terminal No. 6) exhaust gas recirculation valve connector and B-29 (terminal No. 48) engine-ECU connector.

  • Check output line for damage.

Q. Are the check results normal?
Go to Step 11 .
Repair the damaged harness wire.

STEP 11. Connector check: A-33X engine control relay connector

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

STEP 12. Check harness between B-32 (terminal No. 2 and No. 5) exhaust gas recirculation valve connector and A-33X (terminal No. 2) engine control relay connector.
note Before checking harness, check intermediate connector A-13, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 8 .
Repair the damaged harness wire.