DTC P0401 – How To Test Ford F150 EGR

DTC P0401 – How To Test Ford F150 EGR


The Exhaust Gas Recirculation Valve inside of your Ford F-150 is responsible for scavenging exhaust gases from the intake and route them to reduce emissions. Designed to reduce combustion chamber temperatures as well as curbing oxides in your airflow, the EGR is a vital part of your fuel emissions.

When you have a problem with your EGR valve or the EGR system, your Ford truck will turn on your Malfunction Indicator Lamp (MIL) otherwise known as the check engine light. Today we’ll be showing you how to test the electrical wiring harness and the function of your 2007 Ford F-150 EGR. This truck is equipped with the 4.2 liter V6, and the EGR valve is mounted to the side of the intake manifold.


Symptoms of OBDII P0401

  • Poor Idle
  • Bad fuel economy
  • Stumbling acceleration
  • Engine detonation

The Ford EGR system is comprised of several smaller components. When even one of these components fail, it could trigger your P0401 OBDII trouble code. Before you begin our guide on fixing the P0401 engine code, take some time to learn about your Ford EGR and what makes it work.

  1. Actuator Solenoid – What makes the EGR trigger on and off, this solenoid is usually triggered by a switched 5 volt signal.
  2. Differential pressure sensor EGR (DPFE) – This sensor informs the valve and ECU of the pressures on either side of your EGR ports. Properly maintaining this balance is imperative to your EGR’s operation.
  3. EGR Valve – The actual valve that opens and closes the ports on your Ford EGR, this part can become clogged, seized or suffer from poor flow due to carbon deposits.

When you have a trouble code P0401 lighting up your MIL or check engine light, there’s a few possibilities. Before you rip off your EGR and replace it with part number 4F-2Z9D-475-AA, and can be also found under the other interchange part numbers 4F-2Z9D-475-AF or 5F-2Z9-D475-A.

Find your EGR valve in your Ford F-150 engine bay, and check it for any noise or strange behavior when starting.


To test the function of your Ford F150 EGR, you will be using a multimeter to test the wires for power and ground. Unplug your Ford F150 EGR by depressing the retaining pin and unplugging the harness.


If you aren’t sure how to use a multimeter, check out this guide here for a quick lesson. Because the OBDII P0401 means your PCM does not see enough EGR flow, you should always check voltage before replacing anything.


Here’s a look at your Ford F150 EGR connector, and there’s three pins you will need to check. Insert your ignition key and turn to the “ON” position, but do not start your truck engine. Using your multimeter and place your black lead on the negative terminal of your battery. Now gently check the red lead to the PIN 2 shown above, this pin should be a constant 12 volts of power.


If you have a constant 12 volts at this wire, move onward to PIN 3, which is the switched 5 volt signal. Remember that when you are testing any electrical connection, make sure to never depress the testing pin into the connector. Instead always gently touch the metal probe to the metal inside the plastic housing.

The last step of our DIY guide is to check for a low reference ground signal at PIN 1. If there’s a ground present here, chances are that your EGR valve needs replacing and that should be done before you clear the stored code in your OBDII PCM. You now know how to test a Ford F-150 EGR system, use a scan tool to clear your check engine code.

Have any questions about our DIY Guide? leave them for us below and let us know!


  1. Hi prostreetonline thanks for this guide. Wanted to ask because my f150 is still having this code even after testing the circuit and replacing the EGR. is there anything else that could cause the code?

    • Hi Gabriel, thanks for reading.

      Quick question, I am assuming you replaced the Ford EGR all together? Do you have the vacuum hoses connected correctly? And the wiring schematic is correct for your F-150? Please let us know and we’ll be glad to help!

      Thank you for commenting!