How To Test The Ford EGR Valve EGR Vacuum Solenoid, DPFE Sensor How To Test The Ford EGR Valve EGR Vacuum Solenoid, DPFE Sensor How To Test The Ford EGR Valve EGR Vacuum Solenoid, DPFE Sensor

Testing the EGR system on your Ford, Mercury, or Lincoln car or truck is a pretty easy affair. You don't need expensive testing equipment to do it and more importantly, with this article you'll be able to find out exactly what part (of the entire system) is BAD and needs to be replaced and in the process saving time and money.

You'll find step by step instructions on how to test:

  1. EGR Valve
  2. DPFE Sensor
    1. (Delta Pressure Feedback Egr)
  3. EGR Valve Vacuum Regulator Solenoid
  4. Power Circuits

This ‘How To Test’ article covers three different types of Ford EGR DPFE Sensors and below you'll find important info that'll help you to successfully troubleshoot/diagnose the EGR valve code that is lighting up your check engine light. Once you start testing, I recommend you start from TEST 1 and go from there.

En Español Puedes encontrar este tutorial en Español aquí: Cómo Probar la Válvula EGR, el Sensor DPFE, y el Solenoide de Vacío de Ford (at: autotecnico-online.com).

Common Symptoms Of A BAD EGR Valve

The following are the most common symptoms that a Ford (or Mercury or Lincoln) car or truck will usually experience when there's a fault in the EGR System:

  1. Car or truck runs fine, but the check engine light (CEL) is on with an EGR Valve Fault Code:
    1. P0401 EGR System Flow Insufficient.
    2. P01406 EGR Valve Pintle Position.
  2. Rough Idle.
  3. Really BAD gas mileage.
  4. Lack of power as you accelerate the vehicle down the road.
  5. Car (or truck or mini-van) seems to run ok above 30 miles and hour but once you come to an idle, the engine barely stays running and/or idles rough. Once you take off again, it runs OK.

What Tools Do I Need?

Below is a list of must have tools that you'll need to successfully use the testing information in this article to solve the EGR valve system malfunction on your Ford, Mercury, or Lincoln car or truck.

  1. A multimeter (don't have a digital multimeter? Need to buy one? Click here to see my recommendations: Buying A Digital Multimeter For Automotive Diagnostic Testing).
  2. Vacuum pump.
  3. Vacuum gauge.
  4. About two feet of vacuum hose.
  5. A repair manual.
    1. For whatever remove and replace info you'll need that isn't covered by this article.
  6. A Wire-Piercing probe
    1. This tool, which you can attach to your multimeter, is a time-saver. Most of the tests that you're about to perform have to be done with the connector connected to its component... and this tool will come in very handy! If you want to see what one looks like, click here: Wire Piercing Probe

Ford EGR Valve DPFE Circuit Descriptions

Ford EGR Valve DPFE Circuit Descriptions Ford EGR Valve DPFE Circuit Descriptions Ford EGR Valve DPFE Circuit Descriptions

As already mentioned, this article covers three different styles DPFE sensors. Two are bolted onto the engine (one is plastic and the other is metal), and the other is suspended in place just by the two hoses that are attached to it. They all function in the exact same manner. The following circuit descriptions apply to all three DPFE sensors in the image viewer.

  1. Circuit labeled 1:
    1. DPFE Flow Signal
  2. Circuit labeled 2:
    1. Sensor Ground.
  3. Circuit labeled 3:
    1. 5 Volt Reference Voltage.

To make it easy for you to test the particular DPFE sensor on your Ford (or Mercury or Lincoln) car or truck, I have included images of all three types of DPFE sensors with the specific circuit (you need to test) highlighted.

Also, the color of the wires of the DPFE Sensor or EGR Vacuum Regulator Solenoid, on your Ford or Lincoln or Mercury vehicle, will not match the ones in the photos in the image viewer... this is no cause for concern. The circuit descriptions are the same no matter what the individual color of the wires on your Ford (Lincoln, Mercury) car or truck.


Ford EGR Valve Vacuum Solenoid Circuit Descriptions

Ford EGR Valve Vacuum Solenoid Circuit Descriptions

The EGR Vacuum Regulator Solenoid is the second electrical component of the EGR system of your Ford (or Mercury or Lincoln) car or truck that you'll be diagnosing with the help of this article.

The EGR Vacuum Regulator Solenoid is the same no matter what type of DPFE sensor your Ford vehicle is using.

  1. Circuit labeled 1:
    1. Power (12 Volts) Circuit.
  2. Circuit labeled 2:
    1. Solenoid Control Signal from PCM (Powertrain Control Module=Fuel Injection Computer).

The color of the wires on your Ford vehicle will not match the ones in the photos in the image viewer... this is no cause for concern. The circuit descriptions are the same no matter what the individual color of the wires on your Ford (Lincoln, Mercury) car or truck.

Safety Precautions When Testing

Most of the tests that you're about to do are done with your vehicle's engine running (idling). Therefore, it's important that you stay alert, use common sense and take all necessary safety precautions to keep yourself safe.

Also, the EGR valve can get very hot and so you must take care not to burn your hands or fingers.

TEST 1: EGR Valve Vacuum Pump Test

EGR Valve Vacuum Pump Test EGR Valve Vacuum Pump Test

IMPORTANT: To success-fully use this info and correctly diagnose the EGR valve system on your Ford (or Lincoln or Mercury) car or truck do not skip from test to test on your own. Follow the indicated flow of test steps that each test recommends.

The very first thing that we'll do is to verify that the EGR valve itself is working. You'll need a vacuum pump for this test.

This test is done with the engine running, so take all safety precautions.

  1. Remove the vacuum hose from the EGR valve.
  2. Connect a vacuum pump, using a vacuum hose, to the EGR vacuum hose nipple on the EGR valve (see photos in image viewer).
  3. Have an assistant crank up the car (or truck).
  4. Once the engine has started and is idling, apply vacuum with the vacuum pump.
  5. As you apply vacuum, the engine should start to immediately idle very rough and possibly stall.
  6. Now, apply vacuum again with the vacuum pump and hold the vacuum for about a 20 second count.
    1. The vacuum pump gauge's needle should stay steady at whatever number of in.Hg (or kpa) vacuum you have pumped it up to.
    2. If the vacuum pump gauge's needle does not hold steady, but starts to go down to 0 (zero) in.HG, check that the vacuum hose that is connecting the vacuum pump to the EGR valve is making a tight connection on both the EGR valve and the vacuum pump.
  7. When you are sure of your result, turn off the engine.

Let's find out what your test results mean:

CASE 1: If the engine idle grew worse as you applied vacuum with the vacuum pump and the vacuum pump's gauge needle stayed steady, then this result indicates that the EGR valve is working correctly and that the EGR passages in the intake manifold (and in the EGR valve itself) are not blocked with carbon. The next step is to verify that the DPFE sensor is working correctly. Leave the vacuum pump connected to the EGR valve and go to: TEST 2: Testing The DPFE EGR Flow Signal.

CASE 2: If the engine idle grew worse as you applied vacuum with the vacuum pump and the vacuum pump's gauge needle DID NOT stay steady: Verify that the vacuum hose you have connected to both the vacuum pump and the EGR valve is not leaking vacuum and re-do the test.

If after verifying that the vacuum hose is making a tight seal and the vacuum needle on the gauge still drops (after applying vacuum to EGR valve with the engine idling), then this result indicates that the EGR valve's inner rubber diaphragm is torn and leaking vacuum, although the EGR valve is working correctly. Replace the EGR valve and road-test the car or truck.

CASE 3: If the engine idle DID NOT CHANGE as you applied vacuum with the vacuum pump, this indicates one of two things either that 1) the EGR valve is BAD because its rubber diaphragm is torn, or 2) that the EGR exhaust gas passages are blocked in the EGR valve itself, or 3) the inlet EGR orifice on the intake manifold is blocked with carbon. The next step is to remove the EGR valve and bench test it, go to: TEST 3: Bench Testing The EGR Valve.


TEST 2: Testing The DPFE EGR Flow Signal

Testing The DPFE EGR Flow Signal With A Multimeter Testing The DPFE EGR Flow Signal With A Multimeter Testing The DPFE EGR Flow Signal With A Multimeter

Now we're gonna' verify that the DPFE Pressure Sensor is responding to EGR flow into the intake manifold.

Let's get started:

  1. With the vacuum pump still connected to the EGR valve.
  2. Attach the RED lead of the multimeter (using an appropriate tool) to the wire labeled with the number 1 in the image viewer that corresponds to the type of DPFE sensor installed on your vehicle.
  3. Connect the BLACK lead of the multimeter to a good ground point on the engine or to the battery negative terminal.
  4. Select Volts DC on your multimeter.
  5. Have an assistant crank up the car (or truck).
  6. Once the engine has started, notice what the reading is on your multimeter (it should be a value around .9 volts).
  7. After taking note of the voltage value on your multimeter, apply vacuum with the vacuum pump.
  8. As you apply vacuum, the engine should, once again, start to immediately idle very rough and possibly stall.
  9. Now notice the readings on your multimeter as you apply and release vacuum with your vacuum pump.

Now, if the DPFE sensor is working correctly, you'll notice that the voltage reading on your multimeter will increase (to about 3 Volts DC or as high as 4.5 Volts DC) whenever you apply vacuum with the vacuum pump (and of course the engine will idle rough). The voltage will decrease back to the original value recorded at idle and engine idle will return to normal when you release the vacuum applied by the vacuum pump.

Let's find out what your test results mean:

CASE 1: If the voltage reading on the multimeter increased as you applied vacuum with the vacuum pump and decreased when you released the vacuum, then the DPFE sensor is working correctly. The next step is to verify/check the EGR Valve Vacuum Regulator Solenoid. Go to: TEST 4: Testing The EGR Vacuum Regulator Solenoid (Part 1).

CASE 2: If the voltage reading on the multimeter DID NOT increase as you applied vacuum with the vacuum pump and DID NOT decrease when you released the vacuum, then the DPFE sensor is BAD. Replacing the DPFE sensor should solve the EGR fault code issue that is lighting up your check engine light (CEL) on your instrument cluster.

CASE 3: If NO voltage reading at all was displayed on the multimeter as you applied vacuum with the vacuum pump and released it. The next step is to verify that the DPFE sensor is receiving the 5V Reference voltage from the PCM (Powertrain Control Module=Fuel Injection Computer). Go to: TEST 7: Testing The DPFE 5 V REFERENCE SIGNAL.

TEST 3: Bench Testing The EGR Valve

This test step is done with the EGR valve off of the engine. The EGR valve may be hot, so be careful.

The purpose of this test is to verify that when vacuum is applied to the EGR valve, the EGR valve's pintle actually opens and closes. You'll need to blow compressed air thru the inlet opening of the EGR valve, or if you don't have access to compressed air, you can use the ‘good ole’ lungs by blowing air with your mouth.

  1. Remove the EGR valve from the engine.
  2. Connect the vacuum pump once again to the EGR valve using a piece of vacuum hose (see photos in image viewer).
  3. Once the vacuum pump is set up, apply vacuum.
  4. and apply compressed air to the inlet opening of the EGR valve.

Let's analyze your test result:

CASE 1: If you were able to blow compressed air thru' the EGR valve's inlet opening to its outlet side (which is the intake manifold side) when you applied vacuum with the vacuum pump: then the EGR valve's inlet and outlet passages are not blocked with carbon build-up. The next step is to visually check the EGR inlet orifice on the intake manifold to see that it's not blocked with carbon build-up.

If carbon build-up/blockage exists on the EGR inlet orifice on the intake manifold, clean/remove it. Re-install the EGR valve and re-test starting at TEST 1 again.

CASE 2: If you WERE NOT able to blow compressed air thru' the EGR valve's inlet opening to its outlet side (which is the intake manifold side) when you applied vacuum with the vacuum pump: The EGR valve's inlet and outlet passages are blocked with carbon build-up or the EGR valve is BAD. Visually check it for carbon build-up/blockage and if blockage exists; clean and/or remove the carbon build-up. If no carbon build-up exists, then the EGR valve is BAD, replace it.


TEST 4: Testing The EGR Vacuum Regulator Solenoid (Part 1)

Testing The EGR Vacuum Regulator Solenoid (Part 1)

The first part of this test is to verify that the EGR Vacuum Regulator Solenoid is getting getting a good supply of engine vacuum from the intake manifold. Depending on the result of this test, the next test is to check to see if the EGR Vacuum Regulator Solenoid is getting power (12 Volts), in TEST 5.

You can use a vacuum gauge if you want, but it isn't necessary since all we need to ascertain is that engine vacuum is reaching the EGR Valve Vacuum Regulator Solenoid. OK, here's the test:

  1. With the engine off, disconnect the two vacuum hoses that connect to the EGR Valve Vacuum Regulator Solenoid.
    1. These two vacuum lines can be very hard to take off from the EGR Valve Vacuum Regulator Solenoid's nipples, if they have never been removed before.
    2. You have to be very careful as you pull on them since you could break the EGR Vacuum Regulator Solenoid in the process.
  2. Once the vacuum plastic vacuum lines are off, have your helper start the engine.
  3. One of the two vacuum lines/hoses will have engine vacuum.
    1. If the vacuum lines are color coded, the line that is green is the one that usually connects to the intake manifold and is the one that feeds vacuum to the EGR Valve Vacuum Regulator Solenoid.
    2. The other vacuum line is the one that feeds vacuum to the EGR valve once the PCM commands the EGR Valve Vacuum Regulator Solenoid to come on.
    3. If the vacuum lines are not color coded, no big deal... one of the two vacuum hoses/lines will have engine vacuum.

Let's find out what your test results mean:

CASE 1: If engine vacuum was present after the engine was started and was idling, This indicates that the vacuum line is good and delivering the goods to the EGR Vacuum Regulator Solenoid. The next step is now to test the Power Circuit (12 Volt) of the EGR Valve Vacuum Regulator Solenoid, go to: TEST 5: Testing The EGR Vacuum Regulator Solenoid (Part 2).

CASE 2: If engine vacuum WAS NOT present when the engine after the engine was started and was idling: This lack of vacuum will cause the EGR valve not to function and will light up your check engine light (CEL) with an EGR valve fault code. Repairing and/or replacing whatever is necessary to get vacuum to the EGR Vacuum Regulator Solenoid (when the engine is idling) should solve your EGR valve issue on your Ford (or Mercury, or Lincoln) car or truck.

TEST 5: Testing The EGR Vacuum Regulator Solenoid (Part 2)

Testing The EGR Vacuum Regulator Solenoid (Part 2)

The second part of this test is to verify that the EGR Vacuum Regulator Solenoid is getting power (12 volts). The third part (TEST 6) is to test to see if it is allowing vacuum to pass thru' to the EGR valve while you're driving the vehicle. For now, let's make sure its getting juice.

OK, this test can be performed with the EGR Vacuum Regulator Solenoid connected or disconnected from its connector. The test steps assume that you're testing the circuit with the connector connected to the vacuum Solenoid:

  1. Set your multimeter to Volts DC mode.
  2. Connect the RED Lead of the multimeter (with an appropriate tool) to the wire identified with a number 2 in the photos of the image viewer.
  3. Connect the BLACK lead of the multimeter to a good ground point on the engine or to the battery negative terminal.
  4. Have an assistant turn the key on or start the vehicle and notice the voltage reading on the multimeter.

Let's find out what your test results mean:

CASE 1: If 12 Volts were present when the key was turned to On, This indicates that the power circuit is good and delivering the goods to the EGR Vacuum Regulator Solenoid. The next step is now to dynamically test the EGR Valve Vacuum Regulator Solenoid, go to TEST 6: Testing The EGR Vacuum Regulator Solenoid (Part 3).

CASE 2: If 12 Volts were NOT present when the key was turned to On, re-check all of your connections and multimeter setup. If the multimeter still does not register this voltage, you must find out why these 12 Volts are missing. These missing 10 to 12 Volts will cause the check engine light (CEL) to illuminate on your instrument cluster. Repairing the cause should solve your EGR valve issue on your Ford car or truck.


TEST 6: Testing The EGR Vacuum Regulator Solenoid (Part 3)

Testing The EGR Vacuum Regulator Solenoid (Part 3) Testing The EGR Vacuum Regulator Solenoid (Part 3)

The third part of testing the EGR Vacuum Regulator Solenoid is done while road testing your Ford (or Lincoln, or Mercury) car or truck. This test will let you know beyond a shadow of a doubt if the EGR Vacuum Regulator Solenoid is BAD or not.

The engine in your Ford (or Lincoln, or Mercury) car or truck has to be at operating temperature before you start your road-test. This is important, since with a cold engine, the PCM will not activate the EGR valve system.

Here are the test steps:

  1. Disconnect the vacuum line or hose that is connected to the EGR valve (see photo 2 and 3 in the image viewer).
  2. Connect a piece of vacuum hose (that should be about 2 feet in length) to the vacuum line or hose you just disconnected as shown in photo 3.
  3. Snake the vacuum hose under the Hood and secure it under the wiper arm.
  4. Connect a vacuum gauge to the end of the vacuum hose that's under the wiper arm.
  5. The vacuum gauge must be in such a position that you can easily read the gauge's needle as you're driving down the road.

OK, your mission is to verify that the vacuum gauge's needle moves up to 5 in.Hg only when you start to accelerate the car or truck (whether it's from a stand-still or you're already cruising). After the needle moves up to 5 in.HG, the vacuum gauge's needle should always drop down (immediately) to 0 (zero) in.HG when you let go off the accelerator pedal.

Let's find out what your test results mean:

CASE 1: If the vacuum gauge's needle moved up to 5 in.HG when you accelerated the vehicle and then dropped to 0 in.HG when you released the accelerator pedal... this indicates beyond a shadow of doubt that the EGR Vacuum Regulator Solenoid is working correctly.

CASE 2: If the vacuum gauge's needle DID NOT move up to 5 in.HG when you accelerated the vehicle and then dropped to 0 in.HG when you released the accelerator pedal... this indicates that the EGR Vacuum Regulator Solenoid is BAD, replace it.

TEST 7: Testing The DPFE 5 V REFERENCE SIGNAL

Making Sure The DPFE Has Power Making Sure The DPFE Has Power Making Sure The DPFE Has Power

The PCM provides the DPFE sensor with 5 volts so that it can produce a PDFE sensor signal. Without these 5 volts, the DPFE will not work at all. This test step checks for the presence of these 5 volts.

This test can only be done with a multimeter, do not use a test light.

  1. Attach (with an appropriate tool) the RED multimeter lead to the wire labeled with the number 3.
  2. Connect the BLACK lead of the multimeter to a good ground point on the engine or to the battery negative terminal.
  3. Place the multimeter in DC Volts mode.
  4. Have your assistant turn the key to On and notice the voltage reading on your multimeter.
  5. The multimeter should read 5 volts.

Let's find out what your test results mean:

CASE 1: If your multimeter registered 5 Volts: This indicates that the PCM is providing the 5 V REFERENCE Signal to the DPFE. The next step is to verify that the PCM is providing a ground return circuit for these 5 Volts, go to TEST 8.

CASE 2: If your multimeter DID NOT register 5 Volts: Re-check all of your connections and repeat the test. The DPFE sensor will not work without this 5 V REFERENCE voltage and will set an EGR fault code that will light up the check engine light (CEL) on your instrument cluster. Repairing the cause of the missing 5 Volts will solve your EGR valve issue.

Some Tips and Suggestions

It's very rare for the DPFE Sensor to have any type of issue with its 5 V REFERENCE voltage circuit. But if you do encounter this condition and you have triple-checked all of your multimeter's connections and set-up, then the two most likely causes are:

  1. An open short in the wire (that feeds these 5 Volts to the DPFE Sensor) between the PCM and the DPFE sensor.
  2. Or the PCM has fried.

Testing the two above conditions are beyond the scope of this article, but at least you have eliminated the EGR valve, the DPFE sensor, and the EGR Vacuum Regulator Solenoid as the cause of the EGR valve system malfunction.


TEST 8: DPFE Sensor Ground Return

Making Sure The DPFE Has Ground Making Sure The DPFE Has Ground Making Sure The DPFE Has Ground

This test is a continuation of TEST 7... and here you're gonna' test the ground return circuit of the DPFE sensor.

This ground (for the 5 V REFERENCE Signal) is provided by the PCM, so it's crucial that you take the utmost care not to short this circuit to 12 volts as your are testing/verifying it. Use a multimeter for this test and not a test light.

  1. Attach (with an appropriate tool) the BLACK multimeter lead to the wire labeled with the number 2.
  2. Connect the RED lead of the multimeter to the battery positive terminal.
  3. Place the multimeter in DC Volts mode.
  4. Have your assistant turn the key to On and notice the voltage reading on your multimeter.
  5. The multimeter should read 12 volts.

Let's find out what your test results mean:

CASE 1: If your multimeter registered 10-12 Volts: This indicates that the PCM is providing a DPFE sensor ground to the DPFE sensor. If you have gotten to this test by following the following flow of testing: TEST 1, then TEST 2, then TEST 7... then this result indicates that the DPFE sensor is BAD. Replace the DPFE sensor.

CASE 2: If your multimeter DID NOT register 10-12 Volts: Re-check all of your connections and repeat the test. The DPFE sensor will not work without this ground (that the PCM provides) and will set an EGR fault code that will light up the check engine light (CEL) on your instrument cluster. Repairing the issue of this missing ground should solve your EGR valve fault code.

Some Tips And Suggestions

It's very rare for the DPFE Sensor to have any type of issue with its Ground Return Circuit. But if you do encounter this condition and you have triple-checked all of your multimeter's connections and set-up, then the two most likely causes are:

  1. An open short in the wire (that feeds this ground to the DPFE Sensor) between the PCM and the DPFE sensor.
  2. Or the PCM has fried.

Testing the two above conditions are beyond the scope of this article, but at least you have eliminated the EGR valve, the DPFE sensor, and the EGR Vacuum Regulator Solenoid as the cause of the EGR valve system malfunction.

Real Life Case Studies From EasyAutoDiagnostics.com Readers

In this section is input and feedback from all of the folks who have had a similar issue with their vehicle and found a solution. If you're one of them, thank you for sharing your experience with all of us!

If you want to share your repair and/or diagnostic experience, you can use the contact form below.

Real Life Case Study 1

Vehicle: 1998 Ford F150 XLT

Trouble Codes: P0401.

Complaint: P0401

Test Notes/Repair: “i read all of your suggestions and did everything as you stated. i carefully followed all of your tests to get rid of that dreaded PO401 code.

however, after following all of them, what you failed to mention is that inside the throttle assembly there are two small ports from the EGR valve. these ports were clogged completely. i had to remove the throttle assembly and manually clean them. they were closed shut with carbon.

this solved my problem and i'm sure many others would appreciate this as well.

thanks for a great article!!!!!!!”

Courtesy of: Mario (09-19-2014)

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