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Code P1401. DPFE error. Differential Pressure Feedback Sensor

The P1401 code It is related to the DPFE Sensor of your car’s EGR system, and is specific to some brands such as Mazda and Ford. Let’s see more about this fault code, its symptoms, causes and diagnosis.

DPFE is the abbreviation of “EGR delta pressure feedback” whose purpose is to monitor changes in EGR pressure.

All of this may sound very confusing because even many car fans don’t often hear the name DPFE or EGR. But don’t worry, because after reading this you will have a clear idea about this sensor and what it does.

What is a DPFE Sensor?

With advances in technology in the automotive industry, automobiles have seen significant benefits over the years.

A modern car now has many electronic parts and sensors that manage much of its operation. The DPFE sensor is one of them.

As we just mentioned the name, the DPFE sensor is the “EGR Delta Pressure Feedback Sensor”. We will talk about EGR later.

DPFE sensor It is one of the components of your engine that is there to monitor all the air that returns to the air intake through the exhaust.

To improve efficiency, cars use the air coming out of the exhaust, also called exhaust air, to return it. The operation of this can be compared to a turbo system.

The turbo unit contains a turbine inside that runs on the exhaust gases released by your car. This exhaust air drives the turbine, which in turn draws in fresh, colder air from the inlet, much faster and with great force.

Although the DPFE sensor is directly related to the exhaust gases, it does not manage the exhaust air supply. This part is controlled by the EGR system which we will talk about later in this article.

The DPFE sensor, however, is what monitors the pressure difference in the air and the amount of air entering the engine and gives feedback to the EGR system based on the readings. Hence its name.

In a way, the DPFE sensor tells the EGR how much air to let in given the situation.

How Does the DPFE Sensor Work?

DPFE sensor checks exhaust air pressure and pressure changes through an orifice. The output obtained by the sensor is then converted into an analog signal.

This signal is then sent to the car’s computer system to compare with previous readings and manage the EGR accordingly for optimal airflow.

From there, the computer sends a signal to the EGR system to control the exhaust air. The main purpose of the EGR system is to reduce the amount of nitrogen oxide released by the engine as a result of combustion.

As said above, the EGR valve has a feedback sensor called a DPFE sensor. When this sensor goes bad or fails, the P1401 error code is triggered, along with other related trouble codes, which are usually P0140 variants.

The most common symptom is rough idling, which is caused by improper exhaust gas regulation (either too much or too little exhaust is recirculated to the cylinders), which disrupts proper combustion.

You may also be interested in Error Code P1409: EGR vacuum regulator solenoid circuit malfunction

What is Code P1401?

Error code P1401 is defined as a “DPFE (differential pressure feedback sensor) error”.

This code is manufacturer-specific, meaning you won’t see it on all car brands. Rather, it applies only to Ford and Hyundai brands.

Specifications for defining, troubleshooting, and repairs still vary from one make and model to another.

Like other parts, sensors tend to fail eventually. Although rare for such sensors, certain factors can cause them to fail prematurely.

Since the DPFE sensor’s job is to provide an accurate reading to the EGR, when the sensor fails it will give erroneous readings.

If the DPFE sends false signals, the EGR system will not function properly. If the EGR system is not working properly, the PCM valve that controls the amount of air that is mixed with the fuel will begin to mix the air and fuel without precise reference.

Sensor failure will eventually cause the PCM to tilt, thinking that exhaust airflow has decreased. This activates the P1401 code.

Symptoms of Code P1401

These are some of the most common symptoms when the P1401 code occurs.

1. Poor engine performance

If you start to notice that your car starts to idle and shake because of this, it could mean that the DPFE sensor is not working as it should. In such cases, the engine also hesitates when you step on the accelerator and you feel a loss of engine power.

2. Check engine light comes on

If you have the above problems and the check engine light comes on at the same time, it could mean that the engine control unit has detected a problem with the DPFE sensor.

When the check engine light is on, it doesn’t have to be a problem with the DPFE sensor, but it could be.

3. Doesn’t pass the emissions test

This is probably the easiest symptom to find. If your vehicle fails the emissions test, you may have a problem with the DPFE or EGR system.

4. Rough idle

Since there is a mixture outside of specifications, the engine idle speed is affected. Either of these two conditions can occur:

  • Very low idle, with low RPM, irregular, and with a tendency to stall.
  • Very high idle, with high RPM, irregular, and with knocking.

Possible Causes of Code P1401

Among its common causes, we can note the following:

  • Defective DPFE sensor. It is the most common.
  • DPFE sensor harness open or shorted.
  • Bad electrical connection in the DPFE sensor circuit.
  • Damaged PCM, although this is not common.

How to Diagnose and Repair Code P1401

If you have a little knowledge of cars and troubleshooting, you can test the DPFE sensor and its cables yourself at home. Here are some simple things you can check for yourself using a multimeter and a basic knowledge of how to use it.

  1. Check the vacuum hoses: Check for cracks or broken hoses between the EGR and DPFE sensors.
  2. Check the wiring: Check the condition of the wiring, and if there is any damage, breakage, or disconnection. Replace and repair if necessary.
  3. Voltage Test: Use a multimeter and measure the signal, ground, and voltage. Make sure you have 5 volts on the power cord and a proper ground. If the signal/voltage is not in the range of 0.2 to 4.8 voltage, it is a symptom of a damaged DPFE sensor.
  4. Continuity Test: Measure if there is an open or short circuit in the DPFE sensor, with the same multimeter, but this time set to Ohms.
  5. Check the condition of the EGR valve: Check for clogged pipes or a stuck EGR valve.
  6. Check the PCM: The PCM is a rare cause of this error code, but if everything seems fine and you are still experiencing the error code issue, that means your PCM has gone bad. It must be updated before repair, or replaced completely.

Is Code P1401 Serious?

Regarding the operation and driving of the car, the P1401 code has moderate severity. Most of the time you will be able to drive the car until it is taken to the garage or workshop.

Even if the idle is not so irregular, you can drive the car with minimal symptoms. However, we recommend that you take action as soon as possible and repair the fault, so as not to affect other components of your engine and exhaust system.

How Do I Avoid a P1401 Code?

Most sensor problems can be avoided with a periodic inspection of the system. By checking the wiring and condition of the sensor regularly, you can resolve the problem before failure occurs.

However, many times the DPFE sensor becomes damaged without initial symptoms, without warning. In these cases, it will be something that you cannot avoid.

EGR System Operation

The work of the EGR system The exhaust gas recirculation system is to minimize the emission of nitrogen oxide (NOx). This is done by redirecting a small amount of exhaust gas back to the upper intake to mix with the air/fuel charge.

The result is a diluted air/fuel mixture, which means less oxygen per cubic foot. It burns cooler and the combustion chamber temperature is reduced, resulting in lower nitrogen oxide emissions.

For vehicles like Ford and Mazda, the DPFE system is controlled by the PCM (powertrain control module). The system employs the EGR valve, an EVR (electronic vacuum regulator), and a Delta Pressure Feedback (DPFE) EGR sensor.

The DPFE sensor measures the EGR flow through a hole inside the special EGR tube. This hole is located between two hose ports coming out of the tube, which is also connected to the DPFE sensor with special heat-resistant hoses.

If the EGR valve is open, a pressure differential is created across the orifice (Intake Manifold Pressure vs. Exhaust Pressure).

By design, the DPFE sensor measures pressure difference in terms of voltage. The voltage signal output from the DPFE to the PCM is directly proportional to the flow of exhaust gases entering the intake manifold.

EGR valve

The EGR valve, which is short for “Exhaust gas recirculation“, is a mechanism that controls precisely what its name suggests.

The EGR system consists of a valve that controls the exhaust air returning to the engine. The exhaust gases are reused depending on the fuel combustion factors.

The fact is that the fuel and air mixture made by the carburetors or throttle body is not completely burned and is released through the exhaust as 100% unburned gas.

Recirculating this unburned gas ensures that it burns completely again the second time, improving fuel efficiency and, more importantly, controlling the car’s emissions.

An unburned mixture leads to the production of several harmful gases, including nitrogen oxide, which is released into the atmosphere. Therefore, the proper operation of the EGR system has become mandatory in many countries, including Spain.

The EGR system is fairly simple, having a single valve that opens and closes by the amount indicated by the car’s computer.

Older vehicles have mechanical EGR valves, also called pneumatic valves, while modern cars have electronic EGR systems precisely controlled by the vehicle’s computer.

Main functions of an EGR valve

  • Reduce acceleration loss in gasoline engines.
  • Increase engine life by avoiding extreme temperatures while maintaining precise fuel combustion.
  • Reduce vehicle emissions.


You may also be interested in Error Code P1490

As we already mentioned, the P1401 code is not generic and is activated when the DPFE sensor fails in Ford and Mazda brand cars. Its detection is simple since the existence of the code already indicates the location of the fault.

This fault is not serious enough to disable the car, so you can continue driving until you reach a safe place.

If you want to know other articles similar to Code P1401. DPFE error. Differential Pressure Feedback Sensor you can visit the category Fault Codes.


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