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Emissions - Rough Idle/MIL ON/DTC's P0300/P0401



TSB: 01-028/05



2001-2003 Protege (2.0 Liter Engine)


Some vehicles may experience a rough engine idle when stopping at a traffic light and/or MIL illumination. Diagnosis shows that DTC P0300 and/or P0401 are stored in memory when the EGR control valve gets stuck in an open position.

This concern may be caused by Moisture entering the body of the EGR valve causes rust to form on the valve shaft. The rust formation on the shaft causes the valve to stick open intermittently. As a result, too much EGR gas is emitted from EGR control valve and the random misfire occurs.

Customers having this concern should have their vehicle repaired using the following repair procedure.


1. Inspect the function of the EGR control valve using the WDS, referring to the following inspection procedure.

- If the EGR control valve does not work normally, replace it with a modified one and also replace the gasket with a new one at the same time.

NOTE: The gasket cannot be reused, be sure to replace the gasket with a new one during this repair.


1. Connect the WDS to the vehicle.

2. ID the vehicle in the normal manner.

3. Select the "TOOL BOX" and "Datalogger" and press tick.

4. Select the "Module" and "PCM" and press tick.

5. The following screen will display.

NOTE: Erase all of the automatically populated PIDS before starting this testing procedure.

- 1) Select the "BARO" PID and set the display units to "VOLT".

- 2) Select the "EGRCHK #" PID

- 3) Select the "SEGRP #" PID

- 4) Start the Engine

- 5) Press the tick.

- 6) The following screen will display.

As the Number of the STEPS: increases the voltage of the BARO should increase.

NOTE: While performing this step, the engine may stall. This is because the EGR is working normally.

- If the EGR control valve is working normally, the screen will display the following.

Number of the SEGRP @ STEPS: As an increasing Blue line.

Voltage of the BARO: As an increasing Blue line

- If the EGR control valve is NOT working normally, the screen will display the following:

Number of the SEGRP @ STEPS: As an increasing Blue line.

Voltage of the BARO: Will not change and the display will have a Red line

NOTE: Please refer to the following data when you judge the EGR control valve to be OK or NG: (The following Data comes from test vehicles.)

- Number of STEPS: Zero; Voltage of the BARO: 1.1 > 1.3 V.

- Number of STEPS 10; Voltage of the BARO 1.5 > 1.7 V.

- Number of STEPS: 20; Voltage of the BARO: 2.0 > 2.2 V.

- Number of STEPS: 40; Voltage of the BARO: 2.9 > 3.1 V.



NOTE: - This warranty information applies only to verified customer complaints on vehicles eligible for warranty repair. Refer to the Warranty Wizard for warranty term information.

- Additional diagnostic time cannot be claimed for this repair.

Warranty Type: A
Symptom Code: 03
Damage Code: 9Y
Part Number Main Cause: FSY1-20-300-9U
Quantity: 1
Operation Number / Labor Hours: XXB015RX / 0.7 Hrs