Auxiliary Emissions ControlOBD2 Codes

P0406 – Meaning, Causes, Symptoms, & Fixes

Reading Time: 2 minutes

Code P0406 Definition

Exhaust Gas Recirculation Sensor “A” Circuit High

What Does P0406 Mean?

The P0406 code is the result of the exhaust gas circulation (EGR) sensor A having a high circuit voltage. This code is set when the ECM identifies the EGR voltage is higher than the specified range, thus triggering the check engine light to illuminate on the vehicle dashboard.

What Are the Symptoms of Code P0406?

  • Check engine light
  • Increased production of NOx emissions
  • Decreased engine performance
  • Engine stall
  • Engine pinging upon acceleration or higher speeds
  • Lower fuel economy

*No noticeable adverse conditions in some cases

What Causes Code P0406?

  • Faulty EGR valve sensor
  • Open/Shorted EGR sensor circuit
  • Dirty EGR valve
  • Disconnected wiring in EGR circuit

How Sersiou Is Code P0406? – Moderate

This trouble code will not prevent your vehicle from regular operation. Code P0406 has a variety of symptoms that could prevent your vehicle from running normally or increase the difficulty of driving. If this code persists, your vehicle should be capable of being driven to nearest dealership.

Code P0406 Common Diagnosis Mistakes

Prematurely replacing the EGR valve without visually inspecting the wiring of the EGR sensor circuit for disconnection.

P0406 Diagnosis

  • Tools Needed to Diagnose:

How to Diagnosis and Repair Code P0406:

  1. Check to see if there are any other codes along with P0406 and clear your Check Engine Light with FIXD.
  2. Check the freeze frame data for the load and associated temperature of your vehicle upon the code being set.
  3. Conduct a visual inspection of the EGR sensor circuit for shorted or disconnected wiring.
  4. Use FIXD to monitor the EGR while your engine is running and under load.
  5. Remove the carbon buildup within the EGR valve, this might be preventing it from opening or closing properly.
  6. If the problem persists, consider replacing the EGR valve.

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11 Comments

  1. Dumb question; This truck has a diesel engine. Do diesels even have an erg valve?

    1. Absolutely

      1. Hi! I just replace the whole EGR valve now I’m getting the same code p0406 EGR temperature sensor circuit high do I have to replace the EGR temperature sensor also

    2. Have the code po406 I’ve replace the DPFE sensor EGR sensor completely took off the EGR valve make sure there was no carbon in it but on my scanner the voltage on that sensor is 508 constantly if I unplug it or plug it in it is always 508 I’m not real good with electrical but if you can help me out with some kind of explanation that would be wonderful thank you so much

  2. Hi! I just replace the whole EGR valve now I’m getting the same code p0406 EGR temperature sensor circuit high do I have to replace the EGR temperature sensor also

    1. I have same code P0406, I’m going to go look and see what I should do anybody have any ideas for me? Cheapest way to go that’s me

    2. Getting same code. p0406 5.7 300c

  3. Yes, very helpful. You answered my other question as well. Thank You!!!!

  4. i have a dodge ram 1500 2004 i replaced the egr valve but the truck wont start what could be another thing i can check on the truck?.

  5. 2006 f-150 4.6 v8 Had mid fire on #6 replaced coil fixed it Dtove about 15 miles started studdering Now give p108 p302 and p406 codes that didn’t show up before Had no problem before this started I’m lost on what to do Could a part stopped converter cause this?????? Help!!!!!

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