Code No. P0489: Exhaust Gas Recirculation Valve (stepper motor) Circuit Malfunction (earth short)

OPERATION

Power is supplied to the exhaust gas recirculation valve connector terminal from the engine control relay connector terminal.
The engine-ECU connector terminal EGRA, EGRB, EGRC and EGRD makes the power transistor in the unit be in ON position, and that makes currents go on the exhaust gas recirculation valve connector terminal.

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 JUDGEMENT

Check Conditions

Ignition switch is "ON" position.
Battery positive voltage is more than 10 V and is less than 16.5 V.

Judgement Criterion

When the exhaust gas recirculation valve is de-energised, the engine-ECU voltage is less than 1.5 V for 1.4 seconds.

FAIL-SAFE AND BACKUP FUNCTION

None

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. Check exhaust gas recirculation valve (stepper motor) itself.

Exhaust gas recirculation valve (stepper motor) check (Refer to GROUP 17 - Emission Control - Exhaust Gas Recirculation (EGR) System - Exhaust Gas Recirculation Valve (Stepper Motor) Check ).

Q. Is the check result normal?

	Go to Step 2.

	Replace the exhaust gas recirculation valve.

STEP 2. Voltage measurement at exhaust gas recirculation valve connector (power supply line).

(1)Disconnect the connector, and measure at the wiring harness side.

(2)Ignition switch: "ON"

(3)Check the voltage between the exhaust gas recirculation valve connector (power supply line) and body earth.
OK: System voltage

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in power supply line between engine control relay connector and exhaust gas recirculation valve connector.

STEP 3. Voltage measurement at engine-ECU connector (EGRA, EGRB, EGRC, EGRD terminal).

(1)Ignition switch: "ON"

(2)Check the voltage between the engine-ECU connector (EGRA, EGRB, EGRC and EGRD terminal) and body earth.
OK: To initialise, energise exhaust gas recirculation valve for three seconds and de-energise it.

Q. Is the check result normal?

	Go to Step 4.

	Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in EGRA, EGRB, EGRC and EGRD line between exhaust gas recirculation valve connector and engine-ECU connector.

STEP 4. Check of harness damage in power supply line between engine control relay connector and exhaust gas recirculation valve connector.

Q. Is the check result normal?

	Go to Step 5.

	Repair the connector(s) or wiring harness.

STEP 5. Check of harness damage in EGRA, EGRB, EGRC, EGRD line between exhaust gas recirculation valve connector and engine-ECU connector.

Q. Is the check result normal?

	Go to Step 6.

	Repair the connector(s) or wiring harness.

STEP 6. 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 ).