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P0406 – Meaning, Causes, Symptoms, & Fixes

P0406
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What Does Code P0406 Mean?

  • P0406 definition: Exhaust Gas Recirculation Sensor “A” Circuit High
  • Issue Severity: MODERATE – Extended driving with this code may cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible to avoid emission system and catalytic converter damage.
  • Diagnosis: This trouble code will not prevent your vehicle from normal 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 the nearest dealership.

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.

P0406 Causes

There are many potential causes of code P0406.

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

P0406 Symptoms

  • 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

How Do I Fix Code P0406?

With an EGR valve fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0406?

P0406 can be caused by anything from a failed EGR valve to faulty wiring to dirt inside the valve. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0406 code.

Possible Repair Costs for P0406

For error code P0406, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

  • EGR valve: $332 to $413
  • Electrical system diagnosis: $88 to $111

DIY Steps to Diagnose Code P0406

Engine code P0406 could be caused by a number of things, including a bad EGR valve, faulty wiring, or carbon buildup inside the EGR valve. If you’d like to try to fix code P0406 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. This is a beginner-level diagnosis and repair.

DIY difficulty level: Beginner

This repair is suitable for beginners.

Tools/parts needed (our top picks from Amazon):

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Use FIXD to scan your vehicle to verify P0406 is the only code present. If not, make a note of the additional codes, as they help diagnose the problem.

STEP 2: CLEAN EGR VALVE.

Use your car’s service manual to locate and check the EGR valve for any carbon buildup. Check out this video for a visual reference. If you find carbon buildup, use a speedometer cable and throttle body cleaner to remove carbon blocking any air passages. Use FIXD to clear your check engine light. Go for a test drive and see if the check engine light turns back on.

STEP 3: CHECK EGR VALVE WIRING.

Conduct a visual inspection of the EGR sensor circuit for shorted or disconnected wiring.

If the problem persists, consider replacing the EGR valve.

Common P0406 diagnosis mistakes

Prematurely replacing the EGR valve without cleaning it first, or visually inspecting the wiring of the EGR sensor circuit for disconnection.

Still Need Help Fixing Code P0406?

If you’ve followed the steps above and are still experiencing check engine code P0406, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

 

Justin-Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.

About the Author

Justin Hughes

Justin Hughes

Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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