Code No. P0403: EGR Valve DC Motor Malfunction




OPERATION



  • The electric current from the engine-ECU connector terminal EGR+ and EGR- to the EGR valve (DC motor) connector terminal is controlled.

FUNCTION



  • The engine-ECU performs duty control over the EGR valve (DC motor).
  • The engine-ECU performs feedback control over the EGR valve based on the signals from the EGR position sensor.

TROUBLE JUDGMENT


Check Condition
  • Ignition switch is in "ON" position
Judgment Criterion
  • An over current cut-off signal from the EGR valve drive control integrated circuit (IC) is detected.

FAIL-SAFE AND BACKUP FUNCTION



  • The DPF regeneration is prohibited.
  • The throttle valve is opened (Electrical discontinuity).
  • The EGR control is stopped (fully closed).
  • The AS&G control is prohibited.

PROBABLE CAUSES



  • Failed EGR valve
  • Open/short circuit or harness damage in EGR valve circuit or loose connector contact
  • Failed engine-ECU

DIAGNOSIS PROCEDURE


STEP 1. Check EGR valve itself.



  • EGR valve connector check.
  • Check EGR valve itself [Refer to GROUP 17 - Emission Control <DIESEL> - Exhaust Gas Recirculation (EGR) System - EGR Valve (DC motor) Check ].

Q. Is the check result normal?

Go to Step 2.
Repair or replace the connector, or replace the EGR valve assembly.

STEP 2. Check harness between engine-ECU connector terminal EGR+ and EGR valve assembly connector terminal.



  • Check output line for open/short circuit and damage.

Q. Is the check result normal?

Go to Step 3.
Repair or replace the connector, or repair the damaged harness wire.

STEP 3. Check harness between engine-ECU connector terminal EGR- and EGR valve connector terminal.



  • Check output line for open/short circuit and damage.

Q. Is the check result normal?

Go to Step 4.
Repair or replace the connector, or repair the damaged harness wire.

STEP 4. M.U.T.-III diagnosis code



  • After clearing the diagnosis code through M.U.T.-III, start the engine and confirm whether the diagnosis code is set.

Q. Is the 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 ).