P1402 – EGR Function Open (Nissan)

By Reinier (Contact Me)
Last Updated 2022-02-07
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P1402

Table of Contents

1. What Does Code P1402 Mean?
2. Where is the P1402 sensor located?
3. What are the common causes of code P1402?
4. What are the symptoms of code P1402?
5. Get Help with P1402

What Does Code P1402 Mean?

OBD II fault code P1402 is a manufacturer-specific trouble code that is defined by carmakers Nissan and Infiniti as “EGR Function Open”, and is set when the PCM (Powertrain Control Module) detects a malfunction, failure, or defect in the EGR (Exhaust Gas Recirculation) valve, or in its associated systems or circuits that cause the EGR valve to stick in the open position. Note that some sources list code P1402 as it applies to Nissan vehicles, as “EGR System Malfunction Detected (Open)”.

Much of the efficiency of modern internal combustion engines depends on complete combustion of the air/fuel mixture. In practice, this means that when combustion is complete, or nearly complete, more energy can be extracted from the fuel than is possible to do when combustion is poor or grossly incomplete.

This fact forms the basis of modern engine design, but the two greatest downsides of near-complete combustion is a), greatly increased combustion temperatures, and b), the fact that high combustion temperatures cause some of the nitrogen in the intake air to combine with oxygen during the combustion process to create harmful oxides of nitrogen, aka NOx. As a point of interest, NOx is the main ingredient in vehicle exhaust gas that forms smog, the brownish haze that sometimes covers entire cities.

The process of NOx formation happens in nearly all engines*, unless specific measures are introduced to combat the formation of NOx during normal operation of the engine. Note that in gasoline engines, NOx forms at combustion temperatures above 2 370 degrees F, while in diesel engines NOx forms at combustion temperatures above 3 200 degrees F.

*NOx does not form in engines that are fitted with VVT / VCT (Variable Valve Timing / Variable Camshaft Timing) systems because these systems produce the same quenching effect on combustion temperatures as EGR systems do.

Thus, to reduce or eliminate the formation of NOx in modern engines, all EGR systems are designed to route small, but metered amounts of exhaust gas back into the intake system to mix with the inrushing intake air under certain operating conditions, such as during hard acceleration. Since exhaust gas contains almost no combustible material, the presence of the exhaust gas in the air/fuel mixture has a pronounced quenching effect on the combustion flame, which is the mechanism that prevents the formation of NOx during the combustion process.

In terms of operating principles, all EGR systems on Nissan vehicles use dedicated valves that can be controlled either by a vacuum-assisted actuator, or more commonly on newer vehicles, by an electrically operated actuator that is controlled by the PCM. In a fully functional EGR system, the PCM monitors the operation of the engine via several sensors that include, among others, the following-

• engine speed sensor
• engine coolant temperature sensor
• intake air temperature sensor
• EGR valve’s position sensor
• throttle position sensor
• throttle pedal position sensor
• MAF (Mass Airflow) sensor
• MAP (Manifold Absolute Pressure) sensor

When the PCM detects operating conditions that require the activation of the EGR system to limit NOx formation, it commands the EGR valve to open to a degree that will allow only the required amount of exhaust gas to enter the intake system via tubes that are connected to the exhaust system. Note, though, that since the PCM cannot monitor or measure the volume of the exhaust gas that flows through the EGR valve directly, the PCM uses the position of the EGR valve’s moveable pintle to infer the rate of exhaust gas flow. Put differently, this means that the PCM depends on the EGR valve’s position sensor to be fully functional to control the amount of exhaust gas that is introduced in to engine at any given moment.

When current operating conditions no longer require the addition of exhaust gas to the air/fuel mixture, the PCM commands the EGR valve closed. In a fully functional EGR system, the PCM monitors the position of the valve’s pintle via its dedicated position sensor; thus, when the position sensor indicates that the EGR valve is closed, the PCM will conclude that no exhaust gas is being introduced into the engine.

However, in the case of EGR systems, a vast gulf develops between theory and practice when a vehicle starts to age, which means that relatively few Nissan vehicles (or vehicles from other manufacturers, for that matter) have EGR systems that are completely free of defects, faults, or other shortcomings. This is hardly surprising, given the severely deleterious effects that corrosive and soot-laden exhaust gas has on the continued proper functioning of these systems.

In fact, EGR system failures are extremely common on older Nissan vehicles, and when the PCM detects a failure that causes the EGR valve to remain stuck in the open position, it will recognize that it cannot control the EGR system effectively, and it will set code P1402 and illuminate a warning light as a result.

Where is the P1402 sensor located?

This image shows the appearance and location of the EGR valve on a 2005 Nissan Maxima. The large yellow arrow indicates the EGR valve, while the smaller orange arrow indicates the electrical connector that connects the EGR valve to the PCM.

Note, though, that since the appearance and location of EGR valves on Nisan engines vary greatly, we strongly recommend that you consult reliable service information for the affected vehicle to locate and identify the EGR valve correctly.

What are the common causes of code P1402?

The common causes of code P1402 on Nissan vehicles are largely similar across all models, and could include one or more of the following-

• Damaged, burnt, shorted, disconnected or corroded wiring and/or connectors (Common)
• Excessive carbon deposits in the EGR valve that prevents it from closing fully (Common)
• Damaged, split, perforated, or dislodged vacuum lines
• Damaged, broken, or perforated diaphragm in vacuum actuator that prevents the valve from closing fully
• Damaged, defective, or malfunctioning electrically operated actuator
• Damaged, defective, or malfunctioning EGR valve position sensor
• Excessive carbon deposits in the EGR valve that prevents it from closing fully (Common)
• Failed or failing PCM, but note that since this a rare event, the fault must be sought elsewhere before any control module is replaced or reprogrammed

What are the symptoms of code P1402?

Common symptoms of code P1402 on Nissan vehicles are similar across all models and could include one or more of the following-

• Stored trouble code and an illuminated warning light
• Depending on the exact nature of the problem, multiple additional trouble codes might be present along with P1402
• Some readiness monitors may not initiate, or may not run to completion
• The engine may be difficult to start when it is hot
• Varying degrees of power loss may be present
• Fuel consumption may increase dramatically
• The idling speed my fluctuate
• The idling quality may be poor, or the engine may not run at idle at all
• The engine may stall repeatedly, or the engine may stall unexpectedly at low engine speeds
• The exhaust gas may have a strong fuel odor
• The engine may exhibit misfire-like symptoms at some, or all engine speeds and/or loads
• The vehicle will not pass an emissions test

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