DTC P0489: EGR Valve (stepper motor) Circuit Malfunction (ground short)

CIRCUIT OPERATION

The EGR valve power is supplied from the MFI relay (terminal No. 2).
The ECM (terminals No. 31, No. 32, No. 47, No. 48) drives the stepper motor by sequentially turning "ON" the power transistors in the ECM and providing ground to the EGR valve (terminal No. 1, No. 3, No. 4, No. 6).

TECHNICAL DESCRIPTION

The ECM checks whether a short circuit to the ground or an open circuit exists or not by measuring the EGR valve (stepper motor) drive circuit voltage when the current is not flowing through the coil of the EGR valve (stepper motor).

DESCRIPTIONS OF MONITOR METHODS

MONITOR EXECUTION

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)

Exhaust gas recirculation (EGR) stepper motor monitor

Sensor (The sensor below is determined to be normal)

Mass airflow sensor
Engine coolant temperature sensor
Intake air temperature sensor
Barometric pressure sensor
Accelerator pedal position sensor
Manifold absolute pressure sensor

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

Ignition switch is "ON" position.
Battery positive voltage is between 10 and 16.5 volts.

Judgement Criterion

When EGR valve is de-energized, the EGR voltage should be 1.5 volts or less for 1.4 seconds.

OBD-II DRIVE CYCLE PATTERN

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

EGR valve (stepper motor) failed.
Open or shorted EGR valve (stepper motor) circuit, harness damage or connector damage.
ECM failed.

DIAGNOSIS

Required Special Tools:

MB991958: Scan tool (M.U.T.-III Sub Assembly)

MB991824: V.C.I.
MB991827: USB Cable
MB991910: Main Harness A

MB991658: Test Harness Set
MB992110: Power Plant ECU Check Harness

STEP 1. Check harness connector B-114 at EGR valve for damage.

Q. Is the harness connector in good condition?

	Go to Step 2.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 2. Measure the EGR valve motor coil resistance.

(1)Disconnect the EGR valve connector B-114.

(2)Measure the resistance between EGR valve connector terminal No. 2 and either terminal No. 1 or terminal No. 3.
Standard value: 20 - 24 Ω [at 20°C (68°F)]
(3)Measure the resistance between EGR valve connector terminal No. 5 and either terminal No. 4 or terminal No. 6
Standard value: 20 - 24 Ω [at 20°C (68°F)]

Q. Is the measured resistance between 20 and 24 Ω [at 20°C (68°F)]?

Go to Step 3.

Replace the EGR valve. Then go to Step 11.

STEP 3. Measure the power supply voltage at EGR valve harness side connector B-114.

(1)Disconnect the connector B-114 and measure at the harness side.

(2)Turn the ignition switch to the "ON" position.

(3)Measure the voltage between terminal No. 2, No. 5 and ground.

Voltage should be battery positive voltage.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is battery positive voltage (approximately 12 volts) present?

Go to Step 5.

Go to Step 4.

STEP 4. Check harness connector A-30X at MFI relay for damage.

Q. Is the harness connector in good condition?

	Check harness connector A-10 at intermediate connector for damage, and repair or replace as required. Refer to GROUP 00E, Harness Connector Inspection . If intermediate connector is in good condition, repair harness wire between MFI relay connector A-30X (terminal No. 2) and EGR valve connector B-114 (terminal No. 2, No. 5) because of open circuit or short circuit to ground. Then go to Step 11.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 5. Check harness connector B-108 at ECM for damage.

Q. Is the harness connector in good condition?

	Go to Step 6.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 11.

STEP 6. Measure the power supply voltage at ECM connector B-108 by using power plant ECU check harness special tool MB992110.

(1)Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.

(2)Measure the voltage between terminal (No. 31, No. 32, No. 47, No. 48) and ground.

The voltage should be between 5 and 8 volts for approximately 3 seconds when the Ignition switch is turned from the "LOCK" (OFF) position to the "ON" position.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the voltage normal?

Go to Step 8.

Go to Step 7.

STEP 7. Check for open circuit and short circuit to ground between EGR valve connector B-114 and ECM connector B-108.

EGR valve connector B-114 (terminal No. 1) and ECM connector B-108 (terminal No. 31).
EGR valve connector B-114 (terminal No. 3) and ECM connector B-108 (terminal No. 32).
EGR valve connector B-114 (terminal No. 4) and ECM connector B-108 (terminal No. 47).
EGR valve connector B-114 (terminal No. 6) and ECM connector B-108 (terminal No. 48).

Q. Is the harness wire in good condition?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS> or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 11.

	Repair it. Then go to Step 11.

STEP 8. Check the EGR valve operation using special tool MB991658.

(1)Remove the EGR valve.

(2)Connect special tool MB991658 to the EGR valve. (All terminals should be connected.)
(3)Use the jumper wires to connect terminal No. 2 of the EGR valve connector to the positive battery terminal.
(4)Check to ensure that the motor operates when the terminal No. 1 and No. 3 of the EGR valve connector are respectively connected to the negative battery terminal using a jumper wire.

Vibration should be present at each application of voltage to test clip combination.

(5)Then, use jumper wires to connect the terminal No. 5 of the EGR valve connector to the positive battery terminal.
(6)Check to ensure that the motor operates when terminal No. 4 and No. 6 of the EGR valve connector are respectively connected to the negative battery terminal using a jumper wire.

Vibration should be present at each application of voltage to test clip combination.

(7)Reinstall the EGR valve, using a new gasket, and tighten to the specified torque.
Tighten torque: 24 ± 3 N·m [17 ± 3 ft·Ib]

Q. Is the EGR valve operating properly?

Go to Step 9.

Replace the EGR valve. Then go to Step 11.

STEP 9. Check for harness damage between MFI relay connector A-30X (terminal No. 2) and EGR valve connector B-114 (terminal No. 2, No. 5).

note

Check harness connector after checking intermediate connector A-10. If intermediate connector is damaged, repair or replace it. Refer to GROUP 00E, Harness Connector Inspection

. Then go to Step 11.

Q. Is the harness wire in good condition?

	Go to Step 10.

	Repair it. Then go to Step 11.

STEP 10. Check for harness damage between EGR valve connector B-114 and ECM connector B-108.

EGR valve connector B-114 (terminal No. 1) and ECM connector B-108 (terminal No. 31).
EGR valve connector B-114 (terminal No. 3) and ECM connector B-108 (terminal No. 32).
EGR valve connector B-114 (terminal No. 4) and ECM connector B-108 (terminal No. 47).
EGR valve connector B-114 (terminal No. 6) and ECM connector B-108 (terminal No. 48).

Q. Is the harness wire in good condition?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS> or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 11.

	Repair it. Then go to Step 11.

STEP 11. Test the OBD-II drive cycle.

(1)Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0489 set?

	Retry the troubleshooting.

	The inspection is complete.