P0402 Code: Meaning, Symptoms, Causes & Fixing

Modern vehicle models contain an exhaust gas recirculation (EGR) system to control exhaust gas emissions. The EGR system contains three main parts: the EGR valve, EGR solenoid, and DPFE sensor. Your EGR system is controlled by the PCM. A failure in any one of these parts may cause to trigger the P0402 code. This article mainly explains the P0402 code causes, symptoms, and fixing costs.

P0402 Code Definition

P0402 code stands for “Exhaust Gas Recirculation (EGR) Flow Excessive Detected.”

What does the P0402 Code Mean?

The P0402 code indicates that your powertrain control module (PCM) detected the exhaust gas recirculation (EGR) valve is flowing more recirculated exhaust gases than the specified limit.

P0402 code

The exhaust gas recirculation (EGR) system is used to control the emission of exhaust gases. The emission of exhaust gases into the environment spoils the atmosphere and produces different diseases.

The EGR system recirculates a specific amount of exhaust gases into the engine intake to lower the emission of the exhaust gases. The recirculated exhaust gases are used to re-burn in the engine combustion chamber.

This re-burning gas has the following major effects:

  • It decreases the combustion process temperature by lowering the amount of air available in the engine cylinder
  • A reduction in the combustion temperature reduces the production of NOx gasses
  • A reduction in the emission of NOx gases also assists in reducing environmental pollution.  

Your EGR system has different parts, such as the EGR sensor and EGR valve. The EGR valve redirects a specific amount of exhaust gases into the engine cylinder. This valve also helps to reduce the emission of nitrogen oxide (NOx). If any part of the EGR system goes bad, your vehicle will be unable to pass the emission test.

EGR System construction

In the latest vehicle models, the vehicle PCM controls the EGR valve. When the PCM detects that your EGR valve is flowing more recirculated exhaust gases than a fixed limit, it triggers the P0402 code.

Causes of the P0402 Code

  • Bad DPFE sensor
  • Carbon-contaminated EGR valve
  • Bad EGR valve
  • Insufficient vacuum to EGR valve
  • Bad EGR sensor
  • A vacuum leak
  • Faulty EGR connections or wiring
  • PCM-related software problems
  • Bad EGR solenoid
  • Damaged vacuum lines

Symptoms of the P0402 Code

Read More: EGR System Symptoms and Causes

How to Diagnose the P0402 Code

  • Use an OBD-II scanner and record the freeze frame data in order to confirm the existence of the P0402 code.
  • After inspection, clear the codes and perform a test drive. If the P0402 code returns, then move for further inspection.
  • Inspect the vacuum hoses for damage or blockage.  
  • Inspect the EGR valve and EGR passages. If the passages are clogged, clean them properly.
  • Visually inspect the electrical connections and wires connected to the EGR system for damage or corrosion.
  • Inspect the EGR-related sensors (i.e., EGR position sensor, EGR temperature sensor, and EGR pressure sensor).  
  • Properly inspect the EGR control solenoid.
  • Check the exhaust catalyst for damage or unnecessary back pressure on the EGR system.
  • Remove the EGR temperature sensor and EGR valve to inspect for carbon holding the EGR valve open or the EGR bleed port not being blocked with carbon, not permitting the valve to bleed off the vacuum.
  • Properly inspect the PCM.

Common P0402 Code Diagnostic Mistakes

  • Replacing the unnecessary components.
  • Replacing the EGR valve or EGR sensor without inspecting the wiring and connections.
  • Replacing the EGR valve without inspecting the vacuum system for leaks.
  • Installing the new EGR parts without testing them.

How serious is the P0402 Code?

The P0402 code is considered a serious trouble code. This code produces different drivability issues, such as engine stalling or vehicle starting issues. A stalling engine is very hazardous. With this code, you can’t pass the emission test. Driving with this code for a long time may damage the internal parts of your engine. 

P0402 Code Repair Cost

To fix or repair the P0402 trouble code, you need one or more of the following repairs:

PartsCost
EGR valve$220 to $370
EGR pressure sensor replacement$90 to $130
Vacuum leak repair$90 to $220 
EGR valve temperature sensor replacement$210 to $240

FAQ Section

What the P0402 Code Means?

The P0402 code indicates that your powertrain control module (PCM) detected the exhaust gas recirculation (EGR) valve is flowing more recirculated exhaust gases than the specified limit.

What repairs can fix the P0402 code?

  • Replacing the faulty EGR valve
  • Cleaning carbon out of EGR tubes to intake manifold
  • Replacing the damaged catalyst in the exhaust
  • Repairing the damaged or leaked vacuum lines to the EGR valve
  • Replacing the faulty EGR temperature sensor
  • Cleaning the carbon buildup in the EGR temperature sensor
  • Replacing the bad DPFE sensor
  • Updating the software of the PCM

What are symptoms of P0402?

  • Check engine light is illuminating
  • Engine surging on idle
  • Poor engine performance
  • Engine stalling
  • Hard to start the vehicle
  • Failed emission test

Why P0402 Code triggers in Toyota?

The p0402 Toyota triggers due to the following reasons:

  • Bad DPFE sensor
  • Faulty EGR connections or wiring
  • Carbon-contaminated EGR Valve
  • Bad EGR solenoid
  • Bad EGR valve
  • Insufficient vacuum to EGR valve
  • Bad EGR temperature sensor
  • PCM problems
  • A vacuum leak
  • Damaged vacuum lines
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