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DTC P0489: EGR Valve (Stepper Motor) Circuit Malfunction (Ground Short)
 
 
 
 
CIRCUIT OPERATION
  • The EGR valve power is supplied from the MFI relay.
  • The ECM terminals EGRA, EGRB, EGRC and EGRD drives the stepper motor by sequentially turning "ON" the power transistors in the ECM and providing ground to the EGR valve.
 
 
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 coils of the EGR valve (stepper motor).
 
 
DESCRIPTIONS OF MONITOR METHODS
When the EGR valve (stepper motor) drive circuit voltage is under 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.
Judgment Criterion
  • When the EGR valve is de-energized, the ECM voltage should be 1.5 volts or less for 1.4 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None
 
 
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 3 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be stored are: )
  • EGR valve (stepper motor) failed.
  • Harness damage.
  • Connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle Communication Interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite Main Harness A
  • MB992747: V.C.I.-Lite USB Cable Short
  • MB992748: V.C.I.-Lite USB Cable Long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
  • MB991658: Test Harness Set
STEP 1. Measure the EGR valve motor coil resistance.
(1) Disconnect the EGR valve connector and measure at EGR valve side.
(2) Measure the resistance between EGR valve connector terminal power supply line and either terminal EGRA line or terminal EGRB line.
Standard value: 20 - 24 Ω [at 20°C (68°F)]
(3) Measure the resistance between EGR valve connector terminal power supply line and either terminal EGRC line or terminal EGRD line.
Standard value: 20 - 24 Ω [at 20°C (68°F)]
Is the measured resistance between 20 and 24 ohms [at 20°C (68°F)]?
Go to Step 2.
Replace the EGR valve. Then go to Step 8.
 
STEP 2. Measure the power supply voltage at EGR valve motor harness side connector.
(1) Disconnect the EGR valve connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal power supply line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 3.
Repair or replace the connector(s), or check and repair the harness of short to ground and open circuit in power supply line between MFI relay connector and EGR valve connector. Then go to Step 8.
 
STEP 3. Check of short to ground, open circuit and harness damage in EGRA line between EGR valve connector and ECM connector.
Is the harness wire in good condition?
Then go to Step 4.
Repair the connector(s) or wiring harness. Then go to Step 8.
 
STEP 4. Check of short to ground, open circuit and harness damage in EGRB line between EGR valve connector and ECM connector.
Is the harness wire in good condition?
Then go to Step 5.
Repair the connector(s) or wiring harness. Then go to Step 8.
 
STEP 5. Check of short to ground, open circuit and harness damage in EGRC line between EGR valve connector and ECM connector.
Is the harness wire in good condition?
Then go to Step 6.
Repair the connector(s) or wiring harness. Then go to Step 8.
 
STEP 6. Check of short to ground, open circuit and harness damage in EGRD line between EGR valve connector and ECM connector.
Is the harness wire in good condition?
Then go to Step 7.
Repair the connector(s) or wiring harness. Then go to Step 8.
 
STEP 7. 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 power supply line of the EGR valve connector to the positive battery terminal.
(4) Check to ensure that the motor operates when the terminal EGRA line and EGRB line 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 power supply line of the EGR valve connector to the positive battery terminal.
(6) Check to ensure that the motor operates when terminal EGRC line and EGRD line 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 N·m [17 ± 4 ft·Ib]
Is the EGR valve operating properly?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 8.
Replace the EGR valve. Then go to Step 8.
 
STEP 8. 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).
Is DTC P0489 stored?
Retry the troubleshooting.
The inspection is complete.