How to Fix a P0401 Code on Ford (Step by Step – Solved!)

P0401 Code Ford

Do you know how to fix a P0401 Code on a Ford vehicle? this is one of the questions our readers ask a lot. Well, we´ve got you covered.

Many Ford vehicles are notorious for somewhat persistent P0401 code (Exhaust Gas Recirculation Flow Malfunction), which is often a stumbling stone for many repair shops specialized for other makes of vehicles.

This is in general due to the fact that the most common culprit for this code on Ford vehicles is different than the usual suspects on other cars and trucks.

If you are experiencing rough starts of your Ford, and sometimes your engine stalling at high RPMs, very likely you have a P0401 code.

So, how to fix a P0401 code on Ford? To fix the P0401 Code on the Ford vehicle, you just need to follow the steps below:

  • Step #1 Check DPFE sensor
  • Step #2 Check DPFE sensor tubes
  • Step #3 Check EGR ports
  • Step #4 Check EGR solenoid
  • Step #5 Check EGR valve

Meaning: What is the P0401 Code on Ford

The P0401 code stands for the Exhaust Gas Recirculation Flow Insufficient Detected.

EGR or Exhaust Gas Recirculation is a system for decreasing the amount of NOx in the exhaust.

Because NOx is produced at very high combustion temperatures, part of exhaust gases is recirculated back into the intake manifold.

This decreases the amount of fuel-air mixture that can be in a cylinder, which has a consequence of lowering the temperature of combustion.

For this process to happen efficiently a specific flow rate of recirculated gases has to be maintained.

DPFE sensor serves to measure this flow rate, and when it detects that there is a sufficient drop, the P0401 code will be stored.

As the exhaust gases flow through the EGR tube, at one point they are diverted to a hose connected to the DPFE sensor.

Inside of sensor, a diaphragm is passed by flowing gas, and it generates a weak electrical current which ECM interprets as the flow rate.

Based on this measure, ECM is sending a signal to the EGR solenoid, and then the flow rate through the EGR valve is regulated.

If the flow going toward the EGR valve is low enough, it will trigger the code P0401.

Causes of the P0401 Code

On most Ford vehicles the most common problem of insufficient EGR flow is the way that it is measured.

The diaphragm inside the DPFE sensor ages over time and becomes less flexible.

This leads to it measuring the ever-decreasing level of gas flow, even if it were to be constant.

Eventually, due to loss of flexibility, it will “report“ to the ECM the insufficient flow, even though it is sufficient.

In other words, the DPFE sensor will fail and erroneously report the existence of a problem with EGR flow.

The next most common cause of the P0401 code is fouling of the EGR ports on the intake manifold.

Exhaust gases contain various products of combustion and they accumulate on ports that are relatively small, to begin with.

The third most common cause is the rupture of hoses that divert exhaust gases toward the DPFE sensor.

The exhaust gases are hot, while hoses are made of rubber, and repeated warming and cooling of rubber eventually lead to cracks.

Very rarely, the P0401 can be caused by malfunctioning the EGR valve solenoid, but almost never by the valve itself.

Three Most Common Causes of P0401 on Fords >> Check out the video below:

Diagnosis: Reading P0401 Code

As the P0401 is one of the standard ODB-II codes, common on practically all vehicles compliant with ODB-II On-Board Diagnostic standard, reading it on a Ford vehicle is very straightforward.

All you need is any type of ODB-II scanner.

Whether it is one of the fancy professional all-in-one handheld types or a cheep from eBay Bluetooth scanners that connect to your phone, makes no difference.

Depending on the exact type, you will have to the Scan button either on its controls or inside a program.

This will initiate reading of all codes stored as active in the engine’s ECM, and if you have the P0401 it will be displayed in results.

Troubleshooting P0401 Code on Ford (Step by Step)

Troubleshooting the P0401 code on a Ford vehicle comes down to checking the most common causes of it.

Step #1 Check DPFE sensor: To check the DPFE sensor you will need a voltmeter with a back probe.

The back probe you will need to insert into the DPFE sensor connector on the right pin of the three it has and then reconnect the connector.

Next, you should turn the ignition key to ON, but not crank the engine.

Depending on the age of your vehicle it should read between 0.4 and 0.9 Volts, if it is above the sensor is broken and needs to be replaced.

Step #2 Check DPFE sensor tubes: If the sensor voltage reading is fine, you should visually inspect tubes for cracks.

Step #3 Check EGR ports: To check EGR ports you will need to remove the throttle body and shine the light inside the intake manifold.

Looking straight into it, you should see two small holes that could be clogged by carbon buildup that you will have to clean.

Step #4 Check EGR solenoid: Most common problem with a solenoid is that it’s stuck in the open position.

To test this you will need to disconnect both hoses from the solenoid’s two ports, and attach to either of them a spare air hose and simply blow in it.

If you hear the air escaping through the other port, the solenoid is broken.

Step #5 Check EGR valve: To test the EGR valve you will need the vacuum pump with a manometer that you will connect to the port that connects with the solenoid and pump it few times.

If the vacuum doesn’t build up, or it does but then doesn’t hold, the valve is faulty and has to be replaced.

Prevent P0401 Code

The P0401 code happening after a certain time in the life of your Ford vehicle is a reality you will have to accept.

The first and foremost reason for this is the finite life of the DPFE sensor’s diaphragm, which is expected to last around 150,000 miles.

So, if you wish to prevent this code, you can change it every 140,000 to 150,000 miles.

When it comes to fouling of EGR ports, you can inspect them every 50,000 miles or so, and clean them as needed.

Another thing you can do to get ahead of the P0401 code happening is inspecting the DPFE hoses every time you are changing the oil.

Generally speaking, this is the time when you should be inspecting all rubber hoses around your engine bay for visual damage anyway.

Repair Cost of P0401

The cost of repairing the P0401 code on a Ford vehicle depends on the exact cause of it.

If you are taking your vehicle to a professional shop, you can expect some $100-$150 expenses in labor.

Depending on the exact model and year of production of your Ford, you can expect to be charged for parts:

  • DPFE sensor – between $30 and $100
  • EGR solenoid – between $15 and $100
  • EGR valve – between $70 and $500

In general terms, replacement of any of these three parts is relatively simple and can be done in less than 30 minutes, if you are planning to do it by yourself, and you could save few bucks.


The EGR system is a way of decreasing the amount of NOx in exhaust gases by preventing their production during the combustion cycle.

This serves as a measure for “cleaning” the emission.

ODB-II code P0401 happens when the DPFE sensor detects the insufficient flow of exhaust gases.

Such low flow will lead to increased production of NOx, and failing eventual emission testing.

When it comes to Ford vehicles, the most common reason for the P0401 code is not the actual decrease of this flow, but the failure of the DPFE sensor.

As such, it is very easy to fix by replacing the sensor, but in any case, you should also check for other potential causes.

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Jeff is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Reatta. Jeff has been creating written and video content about transportation, automotive, electric cars, future vehicles as well as new, used for more than 18 years. Jeff is based in Boulder, Colorado.

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