P0406 CODE: Exhaust Gas Recirculation (EGR) Sensor A Circuit High Input

In layman's terms, an engine code P0406 is a sign that your car's engine needs to be checked right away. This code is short for Exhaust Gas Recirculation Sensor A Circuit High.

If you ignore this EGR code, then there is a huge certainty that your car's engine will act up soon. You won't be able to drive your vehicle properly, and worse, you'll end up paying for expensive engine repairs. So as soon as you notice the diagnostic code P0406 flash on your onboard computer screen, take your vehicle to a repair specialist at once.

A closer look at OBD2 code P0406

When your car's computer tells you that there is a P0406 code, then it's a problem with the EGR sensor A having a high voltage. When the EOM detects that the EGR voltage is higher than the allowed range, the check engine light will flicker on your dashboard.

What are the possible symptoms of the P0406 code?

A P0406 code comes with a list of symptoms. Take note of the following moment this code flashes on your computer screen.

  • The check engine light flickers –any problem within the car's engine will initiate the check engine light. If this is the only symptom, then you need to probe deeper and let a professional diagnose the P0406 code.
  • Reduced engine performance – a quick and efficient engine starts to stall and make a lot of noise and problems.
  • High noxious emissions present – instead of clean and safe emissions, your car is a noxious gas belcher, and you get called for this on the road.
  • Engine stalls more frequently – your car engine starts to act up and more frequently.
  • Engine pings on top speeds – when driving in top speeds, your car engine starts to stall. You can't go as fast as what you can do before.
  • Poor fuel economy – you're starting to gas up more often, and it's getting too costly to drive your car even to a nearby destination.
  • Take note that some drivers don't notice any of these symptoms, even a check engine light signal. Only the dumbfounding error code is visible on the screen. If this happens, take

    Possible causes of P0406 code

    P0406 is an engine code that could mean problems with the SGR sensor, valve, or wiring. The most common is a problematic EGR valve sensor. In this case, the valve may be replaced, and the problem is fixed soon enough.

    If the problem is due to an open or shorted EGR sensor circuit, then this has to be diagnosed by a technician. Also, the shorted EGR sensor circuit may be completely replaced. And if you need any component or part replaced, rely only on genuine replacement parts. If your vehicle is still under warranty, consult your dealership for genuine replacement parts.             

    P0406 may also be due to a dirty EGR valve. You need to dismantle the valve to clean it using a soft brush, water, and soap. Dry completely before replacing this back inside the engine.  Sometimes a dirty EGR valve may be impossible to clean. For this, replacing the value may be the best option.

    Another uncommon reason for this error code is a disconnected wire on the EGR circuitry. The technician will locate the main EGR circuit and find a disconnected cable. He will clean the wiring/cable attachments before these are replaced on the circuitry.

    Other Troubleshooting Codes about Exhaust Gas Recirculation (EGR)



    Can you drive with code P0406?

    In most cases, a P0406 is not a big deal, and some drivers are still able to drive with their vehicles showing the error code.  But if this error code persists, take your car to your dealership. Has it checked thoroughly before you drive your vehicle?

    How diagnosis and repairs are made

    The diagnosis of code P0406 is made by a technician. He may use special tools and a handbook of your vehicle. If your vehicle comes with a manual, take this with your vehicle to the dealership or car repair specialist.  For the technician to properly diagnose and repair your vehicle, take a photo or screenshot of your dashboard. Consider taking a photo of the load and the temperature of your car when the cone was set.

    Repairs are done gradually as the technician will check for other codes. The check engine light will be cleared. The technician will inspect the EGR to find out if this is shorted or if it's under load. He will also monitor the EGR while the car is running and when it's under load. He will likely clean the EGR valve because this can affect the efficiency of your engine.

    Never overlook P0406 codes and issues. If you are not as tech-savvy, it would be better and safer to take your vehicle to a qualified technician for immediate diagnosis.

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