P0406 Code: Meaning, Symptoms, Causes, & Fixes

The latest vehicles contain an exhaust gas recirculation (EGR) system to control exhaust gas emissions. The EGR system has an EGR valve. The EGR valve regulates the recirculated exhaust gas. The powertrain control module (PCM) triggers the P0404 code when it monitors an issue with the performance of the EGR valve. This article explains the P0406 code causes, symptoms, and fixing.

P0406 Code Definition

P0406 stands for “Exhaust Gas Recirculation Sensor A Circuit High.”

What does the P0406 Code mean?

P0406 code indicates that your powertrain control module (PCM) detects a high voltage signal from the exhaust gas recirculation (EGR) sensor A.

P0406 code

Exhaust gas recirculation (EGR) is an emission control technology used in the latest vehicle models to reduce the emission of NOx.

The main function of the EGR system is to recirculate a definite amount of the exhaust to the combustion chamber to lower exhaust emissions. The emission of nitrogen oxide (NOx) is very hazardous to the environment. Therefore, ERG technology is introduced to control the emission of NOx.

The EGR system is most commonly used in diesel engines. The performance of the EGR system is observed by the powertrain control module (PCM).

Your PCM sets the diagnostic trouble code (DTC) P0406 code when it detects the EGR voltage is higher than the preprogrammed range.

Causes of the P0406 Code

  • Faulty EGR valve
  • Excessive carbon buildup in the EGR valve
  • Carbon buildup in the EGR sensor
  • Open/short EGR sensor circuit
  • Poor electrical connections
  • Damaged or corroded wiring to the EGR valve
  • EGR valve vacuum line leaks
  • Clogged EGR passages

Symptoms of the P0406 Code

  • Check engine light is flashing
  • Engine pinging
  • Your vehicle is unable to pass the emission test because of increased NOx emissions
  • A reduction in the engine performance
  • Engine stall
  • Poor fuel economy

Read More: EGR Valve Parts and Function

How to Diagnose the P0406 Code

  • Use an OBD-II scanner to check the PCM history, pending and existing codes
  • Note the freeze frame data, such as vehicle load, run time, and temperature when the trouble code triggered
  • Clear the PCM memory to clear the codes
  • Perform a test drive. If the P0406 code returns, then perform further inspection to find the root cause of the problem.
  • Visually inspect the connections and wires to the EGR system for damage
  • Inspect the vacuum lines to the EGR system for damage or leak
  • Use a scan tool to check the EGR position on the DataStream with the Key on the Engine running and compare it with the EGR required position. If it looks normal, suspect an intermittent problem.
  • Inspect your EGR valve for carbon accumulation. If your EGR valve is clogged, remove it and clean it properly.
  • Inspect the EGR sensor and EGR valve for damage.
  • Inspect the PCM of your vehicle.

Common P0406 Code Diagnostic mistakes

  • Not properly inspecting all the parts
  • Nor inspecting the wiring and connections
  • Replacing the EGR sensor or EGR valve without inspecting the wiring and connections
  • Replacing the unnecessary components
  • Replacing the EGR valve without inspecting the vacuum system for leaks
  • Installing the new EGR parts without testing them

P0406 Code Repair Cost

The P0406 code fixing or repairing cost depends on the nature of the repair. To fix this code, you need one of the below-given repairs:

Vacuum leak repair$90 to $220 
EGR valve replacement$220 to $370
MAF sensor replacement$180 to $520
EGR temperature sensor replacement$210 to $240
EGR pressure sensor replacement$90 to $130

FAQ Section

How serious is the P0406 code?

The P0406 code is not a serious trouble code. This trouble code indicates an issue with your EGR valve. A faulty EGR valve may increase exhaust gases emission. Exhaust gases are very harmful to the atmosphere. It may also lead to the failure of the engine’s internal parts. Therefore, you should fix the P0406 code as soon as possible.

What repairs can fix the P0406 Code?

  • Repairing or replacing the damaged wires and connections
  • Replacing the damaged vacuum lines
  • Fixing the vacuum line leaks
  • Replacing the bad EGR valve
  • Cleaning the carbon buildup in the EGR passages
  • Replacing the bad EGR pressure sensor
  • Replacing the faulty EGR position sensor
  • Replacing the faulty PCM

Can I drive with code P0406?

Yes, you can drive with the P0406 code. But it is not recommended to drive with this code for a long time.  This code indicates an issue with your EGR valve. A faulty EGR valve may damage the internal parts of the engine.

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