We can help diagnose fault P0400 on your Mercedes vehicle

A1 Diagnostics have all the latest Mercedes equipment and technology needed to diagnose fault codes. Fault codes such as P0400 in Mercedes vehicles and cars can be fully repaired from our garage workshop pictured below.

When you experience a fault like P0400 with your Mercedes vehicle you will get a fault code. This fault code will then explain what the symptoms are and what you need to do to service the vehicle. This month we are going to be looking at Mercedes vehicle fault codes and we start off with P0400.

Mercedes Fault Code: P0400

The P0400 is a MERCEDES-BENZ fault code and is related to the exhaust gas recirculation flow malfunction.

When you get a P0400 Mercedes fault code here are the symptoms and what could be happening.

  • The Battery is flat or dead
  • The EGR volume control valve could be closed when it needs to be able to open and close
  • Faulty Exhaust Gas Recirculation volume control solenoid valve
  • Faulty EGR valve
  • Exhaust Gas Recirculation (EGR) solenoid valve harness is open or damaged
  • Exhaust Gas Recirculation (EGR) solenoid valve has a poor electrical connection
  • Any of the 6 points raised above can be why the P0400 fault code is being displayed, your Mercedes vehicle will need immediate assistance to avoid any further damage to the car.

    We have Mercedes mechanics with over 20 years’ experience servicing P0400 fault codes

    The P0400 fault code is a common occurrence. The P0400 we can diagnose and fix quickly and reliably. We have mechanics that can fix the P0400 fault code that have over 20 years’ experience working in our Mercedes garage, so, when you leave your Mercedes vehicle with us it is in safe hands.


    When you experience a P0400 fault you will need a garage with all the latest vehicle technology to service and repair the fault. A1 Diagnostics have all the technology needed to ensure your Mercedes vehicle is serviced reliably at the most affordable prices.

    If you have any queries or experience a Mercedes fault code get in touch and let us take a look at your vehicle and we will get you back out on the road quickly and efficiently.

    Contact A1 Diagnostics

    Get in touch today for expert advice or to book your vehicle in for an appointment we are happy to help you with any queries you have.

    64 Sloper Road
    CF11 8AB

    Tel: (029 20) 220380
    Fax: (029 20) 223172

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    Mon – Fri: 8:00am – 6:00pm

    Email: info@a1-diagnostics.com