P0401: EGR Sensor A curcuit low

My 2008 Ford f150 4.6 liter v8 is throwing a trouble code: "P0405: EGR Sensor A Circuit Low". I have replaced the EGR, erased the code, and it came back within a few miles. Please note that on this model, the "EGR pressure sensor" (aka: DPFE) is mounted permently on the EGR. Also, the only other component (i am aware of) is the "vacuum regulator". Anyway, I checked the voltage to the EGR, and here are my results — note: all tests are KOEO with the harness plugged into the EGR — (1). BrownWireWithGreenStripe(This is the return to the computer) 0.41 volts.
(2) Bro
Experienced mechanics share their insights in answering this question :
You should clear the codes and monitor the signal return using scanner data for DPFE and disconnect sensor to see if you read between 4 and 5.5 volts. If okay then reconnect sensor and clear the codes. Then cycle key and turn on ignition to run position for more than 5 seconds before starting for PCM to calibrate the DPFE sensor input. Then road test to see if code returns? If code returns then you may have a PCM that is at fault and will need additional pinpoint testing.

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There are many causes for the P0401 trouble code activating. The most common are: Faulty or clogged EGR valve. Low vacuum opening the EGR valve from the EGR control solenoid resulting in the EGR valve not opening all the way.
p0401 Code – Exhaust Gas Recirculation “A” Flow Insufficient Detected | KBB.
Hi There, Code P0401 relates to the EGR valve flow. When this code is triggered, the computer has detected that the flow is insufficient. Driving the car until next week will not cause any harm, although the vehicle may not run well. The EGR valve.
A defective MAP Sensor can cause a lot of issues like displaying P0401 code.
Engine code P0401 could be caused by a number of things, including a clogged EGR valve, a faulty EGR temperature sensor, or an engine vacuum leak.
Engine ping or knock

One of the first symptoms commonly associated with a bad or failing EGR temperature sensor is engine ping or knock. If the EGR temperature sensor malfunctions it will cause issue with the EGR system flow. This can cause cylinder temperatures to rise, which can cause engine ping or knock.

Check engine light: as with most engine management components, a problem with the EGR valve may trigger the check engine light.
One of the most common causes of engine misfires is a faulty EGR valve. The EGR valve is responsible for recirculating exhaust gases back into the combustion chamber. This helps to reduce emissions and improve fuel efficiency. However, if the EGR valve becomes clogged or damaged, it can cause an engine misfire.
Disadvantages of EGR Delete

Some diesel vehicles can experience adverse effects like reduced horsepower, increased exhaust gas temperature and engine knocking. In some cases, it can be more beneficial to have an EGR valve replaced, rather than bypassed.

Spray the EGR valve cleaner onto the carbon deposits. Remove the carbon buildup with the use of a pipe cleaning brush and dull scraper. Repeat the entire process until all of the carbon deposits have been removed. Wipe off the surface using a clean piece of cloth.
The failures are usually caused by a build-up of deposits in the EGR valve over a period of time that causes them to stick. This build-up is part of the ordinary operation of the vehicle and should be regarded as a serviceable item requiring repair or replacement.
This means in the majority of instances there is no requirement to remove the EGR for cleaning and assuming it`s just clogged up / dirty this will resolve the issue. On completion of the job, which takes approximately 45-60 minutes, we`ll reassess the engine management system and reset any fault codes.
Load and engine speed have a direct impact on EGR commands, but MAP, MAF and IAT only have indirect impacts. Speed density systems use air temperature, air pressure and air volume to calculate MAF. The MAP and IAT sensors provide pressure and temperature.
Typically, a vacuum leak will cause situations like hard starting, rough idle, excessive fuel consumption, and engine codes. You might even be able to hear a leak – sometimes a whooshing or whistling sound can be heard with the engine running.
One strategy uses a temperature sensor to measure exhaust flow through the EGR system when the EGR valve is commanded on by the PCM. With this strategy the temperature sensor signal can also identify EGR flow at times it is not wanted such as during engine idling.
If your EGR valve gets stuck in the closed position, then this can lead to a build up of heat within the engine, which can cause the air fuel mix to ignite prematurely. This early combustion, which will be especially noticeable at low revs, is likely to create a knocking sound.
The EGR valve itself is pressure regulated, and needs some form of sensor to be able to send the right amount of exhaust back through the engine. The pressure sensor you are referring to is the component on some vehicles that performs this function.
EGR Fraction Based Control

Critical sensors are an exhaust manifold pressure sensor (P2), an intake manifold pressure sensor (P2) and a speed density estimate of total mass flow. Exhaust and intake manifold pressures are used to control the EGR valve and VGT vanes.

If there`s much dirt and build-up, it`s better to replace it with a new one. Once you`re done cleaning it, place it back in its original position. If the check engine light on the dashboard is switched off, you have successfully cleaned the EGR valve.
Valvoline EGR Cleaner is an effective cleaning spray used to dissolve deposits in the exhaust gas recirculation valve, air intake system, and inlet valves. It helps maximise engine efficiency, allowing it to run smoother and more optimally.
The EGR valve is the main component of the EGR system and it`s normally closed. It connects the exhaust manifold to the intake manifold and is controlled by either a vacuum or a built-in electric step motor.
If your car is running poorly, you may be having problems with your exhaust gas recirculation valve, or EGR. While you can`t test your EGR valve function from home, you can clean it there, a simple task that effectively acts as a repair.
An EGR valve when stuck in an open position not only creates rough idling but sometimes causes the engine to stall while it is idling.
An illuminated Check Engine Light is another symptom of bad or failing EGR valve. If the computer detects an issue with the vehicle`s EGR valve circuit or position, it will set off the Check Engine Light in order to notify the driver of the issue.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

P0401: EGR Sensor A curcuit low
ANSWER : You should clear the codes and monitor the signal return using scanner data for DPFE and disconnect sensor to see if you read between 4 and 5.5 volts. If okay then reconnect sensor and clear the codes. Then cycle key and turn on ignition to run position for more than 5 seconds before starting for PCM to calibrate the DPFE sensor input. Then road test to see if code returns? If code returns then you may have a PCM that is at fault and will need additional pinpoint testing.

Check Engine Light is on. Codes are Bank 1 Sensor 1 Low-voltage, and Bank 2 Sensor 1 Low-voltage. . .
ANSWER : Hi there. What seems to be the issue is the fuel pump is not plugged in. The Oxygen Sensors are working and telling you that the system is too lean with having a low voltage reading. If it was just the upstream sensor, then it would be the wiring, however, both sensors are picking up an issue. This is why the engine is running rough and has no power. If you need further assistance with your vehicle having a loss of power, then seek out a professional, such as one from Your Mechanic, to help you.

I had a p0405 get code replaced egr valve, map sensor,mad sensor, and PCv valve just to be safe but still getting the code why?
ANSWER : The code P0405 and a rough idle is most likely due to carbon getting into the EGR pintle. This will hold the EGR open. When you are getting the rough idle you should shut off engine and remove EGR valve. Check to see if carbon is holding the pintle open. If it is then you will have to remove the carbon from the pintle. Then try and clean out the EGR passages by scrapping them using a round wire brush. Afterwards, start the engine for a few seconds with valve removed to blow out loose carbon. You should then spray a small amount of carbon cleaner into the passages to dissolve the carbon. Lastly, reinstall the EGR and reset the light and codes.

If you’d like assistance with this, consider YourMechanic, as a certified professional can come to the vehicles locations to perform these checks and properly diagnose your Check Engine Light.

EGR code, Cylinder 4 misfire code 0304 detected.
ANSWER : Hi there. The Exhaust Gas Recirculation (EGR) valve may be not designed for the emissions requirements for U.S. standards. If the EGR is pulling from cylinder number 4 and after replacing the EGR and the computer detects a misfire, then the EGR is malfunctioning and not responding. When you close off the tube to the EGR and the EGR light comes on and the misfire light goes out, then the EGR is not responding to your emissions system. I recommend replacing the EGR with the OEM specified part for the engine and all of the issues should go away. If you need further assistance with your misfire and EGR, then seek out a professional, such as one from Your Mechanic, to help you.

Check engine light – O2 sensor circuit + speed sensor circuit…
ANSWER : Hi there. O2 sensor low voltage can be caused my a number of things. Mass air flow sensor was only one of them. It can be a bad O2 sensor, coolant temperature sensor, or wiring issue.

What should be done is a proper diagnosis for the Check Engine Light. Using a complete scanner rather than just a code reader gives a technician the opportunity to not only read trouble codes, but to read voltages for individual sensors. While a code reader tells you the relevant system that set the Check Engine Light on, but with a number of possible causes, the full scan tool allows checking of each individual cause. Having a proper diagnosis will help you have this repaired correctly without replacing parts that are not faulty.

EGR code and Cylinder number 4 misfire detected.
ANSWER : Hi there. The Exhaust Gas Recirculation (EGR) valve may be the wrong one or the cheap design could be not designed for the emissions requirements for U.S. standards. If the EGR is pulling from cylinder number 4 and after replacing the EGR and the computer detects a misfire, then the EGR is wide open and not responsive. It is clearly the EGR as when you close off the tube that the EGR light comes on and the misfire light goes out. I recommend replacing the EGR with the OEM specified part for the engine and all of the issues should go away. If you need further assistance with your EGR and misfire, then seek out a professional, such as one from Your Mechanic, to help you.

I did replace the heater core and two sensor the crank sensor and camshaft sensor it didn’t work can it be the computer
ANSWER : If the check engine light is on, what kind of codes is the system detecting? Do you have spark at the plugs? If you have spark, does spritzing some starter fluid give you a momentary startup? If so, there is a fuel issue. More symptoms and information on the car’s behavior before and after the parts you replaced would be very helpful. At this point, I would recommend an inspection from YourMechanic.com to diagnose this car starting problem, get an accurate assessment of damage and cost estimate for repairs. YourMechanic.com can dispatch a mobile, professional mechanic to your location to help you get your car up and working again.

Car stalls and P0401 insufficient egr flow
ANSWER : The P0401 code is for low EGR flow, but would not be the cause of the stalling if the flow was too low. You also state the problem is when the engine is cold and goes away after it is warm. The EGR system does not start working until the engine is warm.

It sounds like you are having a problem with the transmission or torque convertor. Have a mechanic that knows transmissions check the vehicle when it is cold to see if the engine or transmission is the problem. Sometimes the transmission seals will leak internally causing these problems until the fluid warms up. If you want to have this checked, a technician can diagnose your Check Engine Light and stalling issue thoroughly to determine what repairs will resolve your car problems.