Skip the auto shop - Our mechanics make house calls

P0406 OBD-II Trouble Code: Exhaust Gas Recirculation Sensor "A" Circuit High

check engine light logo

P0406 code definition

P0406 is a general ODB2 trouble code indicating a fault within the exhaust gas recirculation EGR circuit. This code is similar to P0400, P0401, P0402, P0403, P0404, P0405, P0407, P0408, P0409.

What the P0406 code means

P0406 means that the exhaust gas recirculation (EGR) sensor A has high circuit voltage. The ECU detects this high voltage and sets a Check Engine Light. The Check Engine Light will be illuminated on the dashboard.

What causes the P0406 code?

  • Failed EGR valve
  • Excessive carbon buildup
  • Open or short in the wiring harness
  • Poor electrical connection
  • Leak in the vacuum line to EGR valve

What are the symptoms of the P0406 code?

  • In most circumstances the driver may not notice any symptoms other that then illuminated Check Engine Light.

  • Some vehicles may have a slight engine hesitation and fluctuating RPMs.

  • In rare cases the vehicle may have some pinging at higher load and engine stalling.

How does a mechanic diagnose the P0406 code?

  • Uses a scan tool to check for any history, pending and current codes

  • Notes freeze frame data, such as vehicle temperature, run time, and load when the fault occurred

  • Clears the code

  • Performs a test drive trying to duplicate the conditions from the freeze frame data

  • Performs a visual inspection for damaged or worn wiring, broken vacuum lines, and loose electrical connectors

  • Uses the scan tool to view EGR position upon startup and running and manifold pressure

  • Inspects EGR valve for carbon buildup causing it to not open and close properly

Common mistakes when diagnosing the P0406 code

Diagnosis of the P0406 code can be a simple matter or turn into a nightmare if step by step diagnosis is not performed and every step needed completed. This can cause the real problem to be over looked and unneeded repairs performed.

How serious is the P0406 code?

P0406 has a wide range of symptoms that can vary from just the Check Engine Light being on to a vehicle that won't stay running or drives poorly. In vehicles with drivability concerns care should be taken when driving.

The P0406 code should not prevent the vehicle from being driven to a safe location after the fault occurs.

What repairs can fix the P0406 code?

  • Replacing the EGR valve
  • Repairing or replacing wiring harness as needed
  • Repairing poor electrical connections
  • Replacing the vacuum line
  • Cleaning excessive carbon buildup

Additional comments for consideration regarding the P0406 code

In some cases the EGR valve and system may be able to be cleaned. There are specialized cleaners that are used to break up the carbon so it can be cleaned.

Cleaner instructions must be followed but some EGR valves may be able to have the carbon removed and work properly instead of needing replacement.

Need help with a P0406 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Post a question and get free advice from our certified mechanics.

ASK A QUESTION

More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222 code means The manufacturer specifies a range of acceptable voltage to be produced from the throttle position...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P0608 OBD-II Trouble Code: Control Module VSS Output "A" Malfunction
P0608 means there is an malfunction in the vehicle speed sensor A control module often due too faulty speed sensor or shorted electrical wiring.


Related questions

Q: What parts will I need for a timing chain replacement and how many of each. Is my engine interference or non interference?

Hello - your engine does use a timing chain, and that engine is not an interference (valve-to-piston) engine. However, having said that - if the chain breaks, especially at anything above an idle, the broken chain can jam the crankshaft...

Q: Check Engine light and camshaft position sensor code

Hi. If you have a camshaft position sensor code that is coming up, then that is why the Check Engine Light is coming off and on. Most of the time, this is caused by a sensor failure, but it can...

Q: What is the code P0406 and P0128?

The code P0406 is for the electronic gas recirculation valve high circuit input. Meaning the valves sensor is detecting a high voltage input. This can be due to carbon build up on the valve, a bad valve, or a bad...