P0403 Code: Symptoms, Causes & Fixing

The exhaust gas recirculation (EGR) system is a major part of the vehicle. The proper working of the EGR system assists in reducing the emission of the vehicle’s exhaust gases. A reduction in the emission of nitrogen oxide (NOx) gases is very important because these gases are very destructive to the atmosphere in significant amounts. When the powertrain control module (PCM) of your vehicle observes an issue in your EGR system, it sets the P0403 code. This article mainly explains the P0403 code symptoms, causes, and its fixing.

P0403 Code Definition

P0403 code stands for “Exhaust Gas Recirculation “A” Control Circuit.”

What does the P0403 Code Mean?

The P0403 code indicates that your powertrain control module (PCM) detects your engine exhaust gas recirculation (EGR) circuit has malfunctioned.

P0403 code

Exhaust gas recirculation is a principle of emissions control. Your exhaust gas recirculation (EGR) system gets exhaust gases from the exhaust pipe and recycles them into the engine cylinder.

The recirculated exhaust gases minimize the combustion temperature and lower the emission of the exhaust gases. The EGR system also helps to improve engine performance and fuel efficiency. When your PCM monitors an issue with your EGR circuit, it sets the P0403 code to alert the driver.

Causes of the P0403 Code

  • Bad EGR solenoid
  • EGR vacuum line leaks
  • Bad EGR valve
  • Blocked EGR passages
  • Lack of proper electrical signal or vacuum
  • A short in the EGR solenoid
  • A problem with the PCM

Symptoms of the P0403 Code

  • Check engine light illumination
  • Instability when idle
  • Engine misfires (very rare)
  • Engine stalling
  • Poor engine performance
  • Spark knock
  • Failed emission test

How to Diagnose the P0403 Code

  • Use an OBD2 scanner to scan the P0403 code. Record the freeze frame data and use it to verify the main issue.
  • After inspection, clear the codes and perform a test drive. If the P0403 code returns, then move for further inspection.
  • Inspect the vacuum hoses for damage or blockage.
  • Inspect the EGR valve. If the valve is clogged, it them properly.
  • Check the EGR control solenoid.
  • Inspect the EGR solenoid for short.
  • Properly check the electrical connections and wires connected to the EGR system.
  • Check the solenoid connection for corrosion in the connection.
  • Check the EGR pressure sensor, EGR temperature sensor, and EGR position sensor.
  • Inspect the EGR passages for damage or blockage.
  • Properly inspect the PCM.

Common P0403 Code Diagnostic Mistakes

  • Replacing the unnecessary parts
  • Not inspecting the connections and wires
  • Not clearing the PCM memory after fixing the issue
  • Replacing the EGR valve without inspecting the vacuum system for leaks
  • Installing the new EGR parts without testing them
  • Not disconnecting the connection to the EGR control solenoid to check the connection for a corrosion buildup

FAQ Section

How serious is the P0403 code?

The severity level of the P0403 code is moderate. When PCM detects this code, it disables the EGR system and renders it inoperative. The main problem is that your vehicle can’t emission test with this code. Therefore, if an emission test is compulsory in your country/area, you should fix this issue immediately.

What repairs can fix the P0403 code?

  • Replacing the bad EGR valve
  • Replacing the damaged wires to the EGR system
  • Replacing the faulty EGR temperature sensor
  • Replacing the faulty EGR pressure sensor
  • Cleaning the clogged EGR valve
  • Cleaning the carbon buildup in the EGR sensor
  • Replacing the open or shorted EGR vacuum solenoid
  • Replacing the damaged connectors to the EGR vacuum control solenoid

What are the symptoms of DTC P0403?

Read More

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