Infiniti P1402 Trouble Code: Understanding and Solving the EGR Valve Problem

The engine light illuminating on your Infiniti’s dashboard is always a cause for concern. When the diagnostic scanner reveals the Infiniti P1402 code, it indicates a specific problem with the Exhaust Gas Recirculation (EGR) system. This code, often accompanied by a loss of power and rough engine running, is related to the EGR modulation valve circuit. Understanding the origin of this fault, its symptoms, and the methods to resolve it is essential for any Infiniti owner wishing to maintain their vehicle’s performance and longevity. This detailed guide explains everything you need to know to effectively diagnose and treat the P1402 code.

What is the P1402 Code on an Infiniti?

The generic code P1402 is specifically defined as “EGR Modulation Valve Circuit”. It is directly related to the EGR system, a crucial component for reducing polluting emissions, particularly nitrogen oxides (NOx). The EGR system allows a small amount of exhaust gas to be reinjected into the engine’s cylinders. This process lowers the combustion temperature, which reduces the formation of NOx. The EGR modulation valve, often electronically controlled, is responsible for precisely regulating this gas flow. The P1402 code is triggered when the Engine Control Unit (ECU) detects an electrical anomaly in this valve’s circuit, such as abnormal voltage, an open circuit, or a short circuit.

Common Symptoms of the P1402 Fault

When the P1402 code is stored in the ECU’s memory, several symptoms may appear and impair your Infiniti’s driving experience. It is important to recognize them to act quickly.

• Illuminated Check Engine Light: This is the most obvious sign that the ECU has detected an anomaly.
• Decreased Performance and Loss of Power: The engine may lack responsiveness, especially during acceleration.
• Irregular or Rough Idle: The engine may misfire and seem unstable at idle, potentially even stalling.
• Increased Fuel Consumption: A faulty EGR system disrupts the air-fuel mixture, leading to overconsumption.
• Excessive Polluting Emissions: An EGR system failure prevents the control of NOx, which can lead to failing an emissions test.

Possible Causes of the Infiniti P1402 Code

Several issues can be the cause of the P1402 code being triggered. An accurate diagnosis is necessary to avoid replacing parts unnecessarily.

• Faulty EGR Valve: This is the most common cause. The valve itself may be stuck (open or closed) due to carbon buildup, or its electrical actuator may be burnt out.
• Wiring or Connector Problem: Damaged, corroded, loose, or short-circuited electrical wires between the ECU and the EGR valve can cause this code.
• Faulty Differential Pressure Feedback EGR (DPFE) Sensor: This sensor measures the gas flow through the EGR valve. If it sends an incorrect signal to the ECU, it can simulate a valve failure.
• Problem with the Engine Control Unit (ECU): Although rarer, an internal failure of the computer can be the cause.

Diagnosis and Solutions for Resolving P1402

Before proceeding with any replacement, a rigorous diagnostic procedure is recommended.

1. Visual Inspection: Start with a thorough inspection of the wiring and connectors leading to the EGR valve. Look for any signs of damage, corrosion, or poor contact.

2. Electrical Test: Using a multimeter, check the supply voltage and ground of the valve circuit. Also test the resistance of the EGR valve itself by comparing it to the specific values recommended by Infiniti (available in a repair manual).

3. EGR Valve Cleaning: If the valve is simply clogged, a thorough cleaning with a specialized product may be enough to restore its function. Remove it and carefully eliminate all carbon deposits.

4. EGR Valve Replacement: If the electrical test confirms the valve is out of service, its replacement will be necessary. Opt for an OEM quality or certified aftermarket part to ensure longevity and compatibility.

5. DPFE Sensor or ECU Replacement: If the valve and its electrical circuit are intact, test the DPFE sensor. Replacing the ECU is a last resort solution and should be performed by a professional.

Conclusion: Prevention and Cure

The Infiniti P1402 code, although potentially troublesome, is a known and often repairable problem. Regular driving on long trips at high engine RPM can help prevent EGR valve clogging. When faced with this fault, a methodical approach ranging from the simplest inspection (wiring) to valve replacement allows you to restore your Infiniti’s performance and efficiency. If you do not feel comfortable with these procedures, entrusting the diagnosis and repair to a qualified mechanic is the safest solution for an optimal result.