Code P1402 Nissan: Understanding and Solving the EGR Valve Problem
The trouble code P1402 Nissan is an electronic issue related to the Exhaust Gas Recirculation (EGR) system. When the check engine light comes on and this code is stored in the ECU’s memory, it indicates a likely malfunction of the EGR valve or its control circuit. Although often not immediately critical, this problem should not be ignored as it can affect engine performance, increase fuel consumption, and lead to a failed emissions test. This article guides you step-by-step to understand the causes, identify the symptoms, and apply the solutions to effectively resolve the P1402 fault on your Nissan vehicle.
What is the P1402 trouble code on a Nissan?
The generic code P1402 is specifically defined as “EGR Flow Sensor – Circuit Low”. It signals that the Engine Control Module (ECU) has detected an abnormally low voltage in the EGR valve flow or position sensor circuit. The EGR valve is a key component designed to reduce nitrogen oxide (NOx) emissions by recirculating a small amount of exhaust gas back to the intake manifold. In Nissans, this system is electronically controlled, and a malfunction can trigger this code.
Common Symptoms of the P1402 Fault
When the P1402 Nissan code appears, several signs can alert the driver. It is crucial to recognize them to act quickly.
- Illuminated Check Engine Light: This is the main indication. The orange light illuminates on the dashboard.
- Decreased Performance: A noticeable loss of power, especially during acceleration or when going uphill.
- Irregular Idle: The engine may misfire, shake, or stall at idle.
- Increased Fuel Consumption: The engine management system operates in a degraded mode, often with a richer fuel mixture.
- Excessive Emissions: Black smoke from the exhaust may be visible due to an improper air-fuel mixture.
Possible Causes of the P1402 Code
Several elements can be the source of the problem. An accurate diagnosis is essential to avoid replacing parts unnecessarily.
- Faulty or Clogged EGR Valve: This is the most common cause. The valve can be stuck open or closed by carbon deposits.
- Electrical Problem: Damaged wiring, oxidized, or loose connectors leading to the EGR valve.
- Faulty EGR Position Sensor: The sensor that informs the ECU about the actual valve position is out of service.
- EGR Passage Fault: A clogged or leaking intake passage or vacuum hose.
- Problem with the ECU: Although rare, a failure of the engine control unit itself could be the cause.
Diagnosis and Solutions for Resolving P1402
Before changing the EGR valve, follow these diagnostic steps to pinpoint the true cause of the P1402 Nissan fault.
1. Visual Inspection and Cleaning
Start with a thorough visual inspection. Locate the EGR valve (usually mounted on the intake or exhaust manifold). Check the condition of the wires and connectors for any signs of corrosion, burning, or poor contact. Disconnect the electrical connector and inspect the pins. If the valve is accessible, remove it and inspect for carbon buildup. A thorough cleaning with a specialized degreasing product can sometimes solve the problem if the valve is not mechanically damaged.
2. Electrical Tests
Using a multimeter, check the supply voltage and ground of the EGR valve circuit. Consult your Nissan’s repair manual for the specific voltage and resistance values for your model. Also test the valve position sensor. Values outside the specifications will indicate a faulty component.
3. Replacing Faulty Parts
If the electrical tests are good but the valve is physically damaged or irreparably stuck, its replacement is necessary. Opt for quality OEM parts or reputable brands to ensure longevity and compatibility. After replacement, it is imperative to clear the trouble code with a diagnostic tool and perform a road test to verify that the check engine light does not return.
Conclusion: Prevention and Maintenance
The P1402 Nissan code is often the result of a gradual clogging of the EGR system. To prevent its recurrence, it is recommended to use quality fuel and perform regular maintenance. On diesel engines, taking long trips at high engine speeds helps naturally “clean” the system by making it operate at full temperature. Although bothersome, this fault is generally repairable with a rigorous diagnostic method. If you do not feel comfortable with these procedures, entrust the diagnosis and repair to a professional mechanic equipped with the appropriate tools to effectively handle the EGR valve problem.