Mitsubishi P1404 Trouble Code: Everything You Need to Know for an Effective Repair

The illuminated check engine light on your Mitsubishi’s dashboard is often a cause for concern. When the diagnosis reveals the P1404 Mitsubishi trouble code, it specifically relates to the Exhaust Gas Recirculation (EGR) system. This code indicates a malfunction in the EGR valve circuit, more precisely a problem detected in the EGR valve position sensor circuit control. Understanding the causes, symptoms, and solutions is essential to get your vehicle back into optimal running condition and avoid costly repairs.

What is the P1404 Code on a Mitsubishi?

The P1404 code is a generic code related to the engine control system. In Mitsubishi vehicles, it means “EGR Valve Circuit – Performance Problem”. The EGR (Exhaust Gas Recirculation) valve plays a crucial role in reducing nitrogen oxide (NOx) emissions by recirculating a small amount of exhaust gas back to the intake manifold. This helps lower the combustion temperature. The engine control unit (ECU) constantly monitors the position and flow of this valve. When it detects a value outside its expected operating range, it stores the P1404 code and illuminates the malfunction indicator lamp.

Symptoms of the P1404 Fault

It is rare for a P1404 code to appear without noticeable symptoms. The most common signs include:

• Irregular or rough idle: The engine may stall at idle or experience RPM fluctuations.
• Loss of power: A feeling of sluggishness or lack of responsiveness during acceleration.
• Increased fuel consumption: Malfunctioning EGR disrupts the air-fuel mixture.
• Excessive pollutant emissions: Potential failure in emissions tests due to high levels.
• Knocking or pinging sounds: In some cases, incorrect combustion can cause abnormal noises.

Main Causes of the Mitsubishi P1404 Code

Several factors can be the source of this fault. An accurate diagnosis is necessary to identify the correct cause.

• Faulty or clogged EGR valve: This is the most common cause. Soot and carbon buildup can block the valve in an open or closed position.
• Faulty EGR valve position sensor: This sensor informs the ECU about the valve’s position. If it fails, the read values are incorrect.
• Electrical circuit problem: Loose wires, oxidized or corroded connectors, or a broken wire in the valve circuit.
• Faulty differential pressure sensor (DPFE sensor): On some models, this sensor measures EGR gas flow and can trigger the code if it is out of service.
• Problem with the engine control unit (ECU): Although rare, an internal ECU failure can send incorrect signals.

Diagnosis and Solutions for Repairing P1404

Before replacing expensive parts, a methodical diagnostic procedure is recommended.

1. Visual Inspection and Cleaning

Start with a thorough visual inspection. Locate the EGR valve (usually attached to the intake or exhaust manifold). Check the condition of the electrical connectors and hoses. Remove the EGR valve and inspect its level of clogging. A thorough cleaning with a specialized EGR circuit cleaner can often solve the problem if the valve is not mechanically damaged.

2. Electrical Check

Using a multimeter, check the supply voltage and the continuity of the wires between the valve and the ECU. Also test the resistance of the EGR valve solenoid or position sensor, comparing the measured values with those specified in your Mitsubishi’s workshop manual.

3. Replacing Faulty Parts

If cleaning and electrical checks haven’t worked, replacement is the solution.

• Replace the EGR valve: Choose an OEM quality part or a good quality aftermarket part to ensure longevity and compatibility.
• Replace the position/flow sensor: If electrical tests have identified it as faulty.

4. Resetting the Code

After the repair, use an OBD2 diagnostic tool to clear the P1404 code from the ECU’s memory. Perform a road test to ensure the fault does not reappear and that the symptoms have completely disappeared.

Conclusion: Prevention and Maintenance

The Mitsubishi P1404 code is a serious warning that should not be ignored. Although often related to clogging, it requires intervention to avoid damaging other engine components and to ensure controlled emissions. Regular high-speed driving on the highway can help prevent EGR system clogging by allowing more complete combustion and avoiding the buildup of carbon deposits. Regular maintenance and the use of quality fuels remain your best allies in avoiding this type of breakdown.