How to Fix P0406 Code: Causes and Solutions

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EGR valve

If your Check Engine Light comes on, knowing the root cause is essential. Plug in your OBD-II reader to find the error code. If it comes up with a P0406, don't worry - we're here to help. Continue reading as we discuss the causes and fixes for this code. Let's get started!

What is Code P0406?

The P0406 is an emissions-related trouble code for Exhaust Gas Recirculation (EGR) Sensor "A" Circuit High. This diagnostic trouble code is set when the EGR position sensor sends a signal to the Powertrain Control Module (PCM), indicating that the EGR voltage is higher than the allowed limit.

Symptoms of Code P0406

While having this issue on your vehicle, you may experience some of these symptoms:

  • Increase in combustion temperatures
  • Malfunction indicator lamp (MIL) is on.
  • Vehicle surging while driving
  • Vehicle stalling

Causes of Code P0406

A few primary causes in any vehicle can create a P0406 trouble code. Most of the common reasons are:

  • Shorted EGR sensor signal circuit
  • Damaged wiring harness
  • Failure of EGM sensor or solenoid
  • Corroded EGR valve
  • Leaking vacuum hoses
  • PCM failure

How to Diagnose Error Code P0406?

Diagnosing the issue is crucial when fixing any diagnostic trouble code issue. This ensures that every possible cause is checked and avoids damaging other parts or systems while fixing the original problem. To properly diagnose a P0406 code, these are the steps you need to follow:

  1. Connect your OBD-II scanner to the vehicle's diagnostic port and check for other codes related to the P0406 code. Don't forget to clear the codes after scanning.
  2. Check the EGR valve for any physical damage, and clean it if necessary.
  3. Inspect all hoses and vacuum lines connected to the EGR valve for leaks. Replace any damaged or leaking hoses.
  4. If the EGR valve tests good, then the next step is to check the wiring harness and connectors going to the EGR valve. Ensure there are no loose, damaged, or corroded connectors or wires.
  5. If everything looks good, the last step is to check for any carbon buildup on the EGR valve. Clean the EGR valve if necessary.

How to Fix Code P0406?

If you have done all the fixes above, but the problem persists, the only solution is to replace the EGR valve. If you are uncomfortable replacing it yourself, you can have it done by a professional. However, if you are confident enough with your skills, you can replace the EGR valve by following these steps:

Step-by-Step to Replacing the EGR Valve

  • For safety purposes, disconnect the negative battery.
  • Locate the EGR valve. It is located on the engine near the firewall.
  • Remove the bolts that secure the EGR valve to the intake manifold.
  • Pull out the old EGR valve and install a new one in its place. Ensure that the new valve is seated correctly.
  • Reattach the bolts that secure the EGR valve to the intake manifold and tighten them.
  • Reconnect the negative battery cable 
  • Start your ignition.

Common Mistakes When Diagnosing the Code P0406

When diagnosing error code, there are instances that you may end up making some common mistakes. But if you would be careful and take extra precautions, you should avoid making these mistakes:

  • Not checking the EGR valve itself. You should always check the EGR valve first before anything else. There are instances when the problem lies with the valve and not with the sensor.
  • Not cleaning the carbon buildup in the EGR port.
  • Not testing all modes and cycles of the EGR system
  • Not checking for other codes that may be stored along with the P0406 code
  • Replacing parts without first testing them

Code P0406 FAQs

1. Is the P0406 code serious?

The P0406 code is serious because it can cause your vehicle to fail an emissions test. 

2. Can I drive with the P0406 code?

Yes, you can still drive having this issue. However, it is not recommended to continue driving if you experience drivability issues.

3. How much does it cost to fix the code P0406?

There is no definitive answer as to how much it will cost to repair this issue. The repair cost will depend on what is causing the P0406 and the severity.

4. How much is the EGR valve?

The cost of the EGR valve will depend on the make and model of your vehicle. The ideal charge is between $250 to $350 for the part itself.

5. Do I need professional help to diagnose this error code?

It is possible to diagnose and repair this code without professional help with the help of our guide. However, it is always recommended to have a professional inspect your vehicle if you are unfamiliar with the inner workings.


That’s it! If P0406 is triggered on your OBD scanner, don’t fret! Hopefully, this article will help you in fixing this error. In most cases, the solution to rectifying this trouble code can easily be fixed by anyone. However, if you're uncomfortable doing the repairs yourself or don't have the time, we recommend taking your vehicle to a qualified mechanic. 

How did it work for you? We want to know your thoughts! If you need more help with your car, check out our other blog posts or contact us today. Happy driving!