Few vehicle-related issues can be rather as maddening together the sudden illumination that a inspect engine light. Problems of this form arise because that a variety of reasons, despite the vast bulk relate come operational or emissions failures. In essence, the beginning of a check engine irradiate is a vehicle’s means of calling attention to an problem that is at hand.

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When a examine engine light appears, a vehicle’s ECM stores a corresponding DTC (diagnostic trouble code). This codes offer as general indicators that the malfunction that has been detected. DTCs are noted numerically, v the addition of an alphabet prefix.

One such example is password P0402, i m sorry is relatively common throughout numerous makes and models the vehicles. In the vast bulk of cases, DTC P0402 does not indicate a major mechanical or electrical failure and also can it is in remedied in short order, if properly diagnosed.

In most cases, an afternoon of TLC is all that is essential to regain your car to proper running order. Check out on to learn more about trouble password P0402, and how to remedy such an issue, must it current itself.

Table the Contents

How come Fix

What Does password P0402 Mean?

OBD-II Trouble code P0402 Description
Excessive EGR Flow

DTC P0402 shows that extreme or improperly time exhaust gas circulation is being permitted to recirculate into the intake manifold the the affected vehicle’s engine. Together a result, the vehicle’s ECM has registered an emissions-related DTC (P0402).

To far better understand the definition behind a P0402 fault code, one must very first familiarize themselves through the principles of EGR valve operation.

In the 1970s, a hold of anti-smog legislation was passed right into law, thereby mandating the palliation of emissions output by production vehicles. Together a result, automotive manufacturers started experimenting v various means of reducing exhaust-related pollutants. One such method, which verified successful, is the idea of EGR (exhaust gas recirculation).

This principle centers around the recycling that exhaust gasses, into an engine intake tract, in a bid to burn every combustible materials, in as finish a fashion together possible. Solution of this form rely upon EGR valves to meter the amount of exhaust gasses recirculated right into an engine intake.

When an engine is not up to operating temperature, a properly operating EGR valve need to restrict the recirculation that exhaust gasses. However, one EGR valve should progressively open together an engine warms, in order to reducing emissions output.

When a P0402 DTC has actually been set, a vehicle’s ECM has identified that an excessive volume the exhaust gasses have been introduced right into the engine’s intake tract.

Related DTC: code P0401, password P0404

Symptoms of password P0402

Numerous symptoms are connected with the start of a P0402 diagnostic trouble code. However, this symptoms often vary on a case-by-case basis and also might differ dramatically from one do or design of automobile to the next.

The complying with are the most typical symptoms associated with DTC P0402.

Rough, or rough idle

Causes of code P0402


In the vast bulk of cases, remedying the root reason of a P0402 diagnostic trouble code is no as daunting as one might initially believe. However, the effectiveness of this repair procedure hinges top top one’s ability to assess the problem at hand and make an accurate diagnosis.

The complying with steps will aid you in addressing the root reason of her vehicle’s P0402 trouble code.

#1 – examine For extr DTCs

Before start the diagnostic process, usage a quality OBD-II scan tool to check for the existence of additional DTCs. Closely diagnose any type of additional active codes, in a bid to preeminence out a connection with the offending P0402 DTC.

#2 – Visually check All related Wiring and Hoses

Next, friend will perform a mindful visual inspection of every vacuum hoses and electrical connectors which exchange mail to your engine’s EGR valve.

Check each attached vacuum hose for any type of signs of dry-rot, cracks, or evident deterioration. Replace any type of such hoses that are uncovered to it is in defective.

You should also inspect any kind of wiring i beg your pardon connects come the engine EGR valve, for division or indications of chafing. Any kind of damage the is found should be repaired immediately.

#3 – eliminate EGR Valve Mounting Hardware

If a test journey confirms the reoccurrence of DTC P0402, visual inspection of the engine’s EGR valve will certainly be necessary. In bespeak to perform so, all corresponding fasteners have to be gotten rid of from the EGR valve’s mounting flange.

If heavy carbon accumulation is found approximately the EGR valve’s plunger, together deposits deserve to be removed with the usage of a pipe clean brush and throttle body cleaner.

#4 – check Vacuum Actuated EGR Valve

If her vehicle’s engine features a vacuum-actuated EGR, a vacuum pump have the right to be offered to test unit functionality. This pump should be plumbed to the EGR valve’s vacuum nipple, and also a slight vacuum must be applied.

If the valve’s plunger does no actuate, the EGR valve is come be considered suspect.

#5 – check Electronically Actuated EGR Valve

If your automobile features one electronically actuated EGR valve, a bi-directional scan tool can be supplied to validate the unit’s operation. V a scan device of this nature hooked come the vehicle’s OBD-II data port, the EGR valve can be commanded come a collection position.

If no plunger actuation is noted, an electric circuit fault, or EGR motor error is to blame. Further electric testing will certainly be necessary.

#6 – inspect Live Data

If EGR valve functional experimentation has revealed no issues, you have to consult live streaming data from your engine’s sensors, in a bid come secure a diagnosis. Prior to beginning this process, reinstall your engine’s EGR valve, torqueing all previously removed hardware.

With the usage of an OBD-II scan tool v live data capabilities, monitor all EGR-related temperature and pressure signals, if comparing gathered data to the manufacturer mentioned values.

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Replace any sensor that is reputed faulty during this process. If DTC P0402 persists, attention need to turn to the vehicle’s ECM programming.