P0490

DTC P0490: EGR Value (Stepper Motor) Circuit Malfunction (Battery 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 power supply exists or not by measuring the EGR valve (stepper motor) drive circuit voltage when the current not flowing through the coils of the EGR valve (stepper motor).

DESCRIPTIONS OF MONITOR METHODS

When the EGR valve (stepper motor) drive circuit voltage is over the specified range, it is judged that a malfunction exists.

MONITOR EXECUTION

Continuous

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

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

- 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

- Manifold absolute pressure sensor

- Accelerator pedal position sensor

DTC SET CONDITIONS

Logic Flow Chart






Check Conditions

- Ignition switch is "ON" position.

- Battery positive voltage is at between 10 and 16.5 volts.
Judgement Criterion

- When the EGR valve is energized, the ECM voltage should be 6.7 volts or more for 1.4 seconds.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3 Monitors, Trips, Drive Cycles and Readiness Codes.

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

- EGR valve (stepper motor) failed.

- Harness damage.

- 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

STEP 1. Check harness connector B-12 at EGR valve and harness connector B-10 at ECM for damage.

Q. Is the harness connector in good condition?

YES Go to Step 2.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 5.
STEP 2. Measure the EGR valve motor coil resistance.

(1)Disconnect the EGR valve connector B-12.





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

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

YES Go to Step 3.

NO Replace the EGR valve. Then go to Step 5.

STEP 3. Check for short circuit to power supply between EGR valve connector B-12 and ECM connector B-10.

Q. Is the harness wire in good condition?

YES Then go to Step 4.
NO Repair it. Then go to Step 5.
STEP 4. 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: 23 ± 6 Nm [17 ± 4 ft-lb]

Q. Is the EGR valve operating properly?

YES Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 5.

NO Replace the EGR valve. Then go to Step 5.

STEP 5. 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 Monitors, Trips, Drive Cycles and Readiness Codes.

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

Q. Is DTC P0490 set?

YES Retry the troubleshooting.
NO The inspection is complete.