Code No. P0403: EGR Valve DC Motor Malfunction

OPERATION

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

FUNCTION

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

TROUBLE JUDGEMENT

Check Condition

Ignition switch is in "ON" position

Judgement Criterion

An over current cut-off signal from the exhaust gas recirculation valve drive control integrated circuit (IC) is detected.

FAIL-SAFE AND BACKUP FUNCTION

The throttle valve is opened (Electrical discontinuity).
The EGR control is stopped (fully closed).

PROBABLE CAUSES

Failed exhaust gas recirculation valve
Open/short circuit or harness damage in exhaust gas recirculation valve circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check exhaust gas recirculation valve itself.

Exhaust gas recirculation valve connector check.
Check exhaust gas recirculation valve itself [Refer to GROUP 17 - Emission Control <DIESEL> - Exhaust Gas Recirculation (EGR) System - Exhaust gas recirculation valve (DC motor) Check <4D5>].

Q. Is the check result normal?

	Go to Step 2.

	Repair or replace the connector, or replace the exhaust gas recirculation valve.

STEP 2. Check harness between engine-ECU connector terminal EGR+ and exhaust gas recirculation valve 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 exhaust gas recirculation 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 ).