Nissan Fault Code P1402: Diagnosis, Symptoms, and Solutions for the EGR Valve

The engine light illuminating on your Nissan’s dashboard is often a cause for concern. Among the common error codes, Nissan P1402 is specifically related to the Exhaust Gas Recirculation (EGR) system. This code indicates a problem with the Differential Pressure Feedback EGR (DPFE) sensor circuit or the EGR valve itself. Understanding this fault, its causes, and the repair methods is essential for any owner or mechanic looking to resolve the issue effectively and avoid costly repairs. This article guides you step-by-step through diagnosing and fixing the P1402 code on your Nissan vehicle.

What is the P1402 fault code on a Nissan?

The P1402 code is a generic code related to the engine control system. It is defined as “EGR System – Differential Pressure Feedback Sensor Circuit Low.” Essentially, the onboard computer (the Engine Control Unit or ECU) continuously monitors the flow of recirculated gases through the EGR valve. To do this, it uses a differential pressure sensor (DPFE or Delta P) which measures the pressure difference between the two sides of the metering orifice the gases pass through. The Nissan P1402 code is triggered when the ECU detects that the electrical signal from this sensor is abnormally low, outside the expected voltage range. This means the system perceives an insufficient or non-existent EGR gas flow.

Common Symptoms of the P1402 Fault

It is rare for the P1402 code to be the only sign of a problem. It is usually accompanied by physical symptoms that the driver can feel:

• Illuminated Check Engine Light: This is the most obvious sign.
• Rough or Unstable Idle: The engine may stall at idle or have hiccups.
• Loss of Power: A feeling of sluggishness during acceleration, especially when the engine is under load.
• Increased Fuel Consumption: Malfunctioning EGR disrupts the air-fuel mixture.
• Reduced Performance: The vehicle generally lacks responsiveness.
• In some cases, no noticeable symptoms appear other than the warning light, especially in the early stages of the fault.

Main Causes of the Nissan P1402 Code

Several components can be the source of this fault code. It is crucial to investigate them in a logical order to avoid replacing parts unnecessarily.

• Faulty or Clogged EGR Valve: This is the most common cause. The valve, which is a mechanical actuator, can become stuck in the open or closed position due to the buildup of soot and carbon.
• Faulty DPFE Sensor: The differential pressure sensor itself may be faulty and sending an incorrect signal to the ECU.
• Electrical Circuit Problems: Cut, unsoldered, corroded, or short-circuited wires between the sensor and the ECU can cause this code.
• Disconnected Connections or Plugs: A simple loose connection or an oxidized connector can interrupt the signal.
• Clogged Measurement Orifices: The small rubber hoses connecting the DPFE sensor to the EGR system can be clogged with deposits, preventing a correct pressure reading.
• Problem with the Engine Control Unit (ECU): Although rare, an internal failure of the computer is a possibility to be ruled out as a last resort.

Diagnosis and Solutions for Fixing P1402

Before replacing anything, a methodical diagnosis is essential.

1. Visual Inspection and Cleaning

Start with a thorough visual inspection. Locate the EGR valve (often on the intake manifold) and the DPFE sensor (usually attached to it or nearby). Check the condition of the wiring and connectors for any signs of corrosion, burning, or damage. Inspect the small rubber hoses to ensure they are not punctured, kinked, or clogged. Remove the EGR valve if possible. If it is stuck due to a thick buildup of carbon, a thorough cleaning with a specialized EGR degreaser may sometimes be enough to solve the problem.

2. Electrical Tests with a Multimeter

If the visual inspection reveals nothing, move on to electrical tests. Using a multimeter, check the supply voltage and ground of the DPFE sensor connector (refer to the Nissan repair manual for precise values). Also test the signal wire. A faulty sensor will often show a signal value that is out of specification (too low for the P1402 code) or does not vary when the engine is running.

3. Replacing Faulty Parts

Depending on your findings:

• If the EGR valve is stuck and impossible to clean: Replace it with a new or quality remanufactured part.
• If the DPFE sensor is faulty: Replace it.
• If the wiring is damaged: Repair or replace the faulty wires.

After any repair, clear the fault code with an OBD2 scanner and take a test drive to ensure the warning light does not reappear.

Conclusion: Prevention and Maintenance

The Nissan P1402 code is a serious but often repairable problem without resorting to an expensive garage if you have some mechanical skills. An accurate diagnosis is key to avoid replacing the wrong part. To prevent clogging of the EGR system, which is the root cause of many problems, prioritize regular drives at high engine speeds (on the highway) which help to naturally “clean” the system by making it operate fully. Quality engine oil and premium fuels can also reduce the formation of carbon deposits.