Fault code P0401 is called “Exhaust Gas Recirculation (EGR) “A” Flow Insufficient Detected” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0401
This Diagnostic Trouble Code (DTC) is a general powertrain code. Error P0401 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.
EGR is responsible for exhaust gas recirculation. It is part of the vehicle’s exhaust emission system. It is used to reduce temperature, combustion pressure, and to control nitrogen oxides.
Typically, an exhaust gas recirculation system consists of three parts:
- The exhaust gas recirculation valve.
- Solenoid actuator.
- An exhaust gas recirculation differential pressure sensor (DPFE).
They work together to provide the correct amount of recirculation depending on engine temperature, load, etc.
Code P0401 means that the OBD has detected insufficient exhaust gas flow in the intake manifold. When the engine exhaust gas recirculation system valve is opened.
Symptoms of vehicle malfunctions
The main signal that an error P0401 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The Check Engine light on the control panel will illuminate (the code will be written to the ECM memory as a fault).
- The vehicle’s engine may run erratically under load or at high speeds.
- Increased emissions of harmful substances in the exhaust.
- There may be other symptoms as well.
A faulty exhaust gas recirculation valve is often the cause of excessive ignition of the fuel mixture. This, in turn, can cause damage to the engine pistons and valves. Therefore, it is advisable to correct the problem associated with fault P0401 as soon as possible.
Factors that can cause this error code
The error code P0401 can mean that one or more of the following problems have occurred:
- DPFE sensor (EGR differential pressure feedback) is defective and needs to be replaced.
- The exhaust recirculation pipe is clogged, most likely a buildup of carbon monoxide.
- Exhaust gas recirculation valve is defective.
- Due to lack of vacuum, the exhaust recirculation valve cannot open.
- The exhaust recirculation system temperature sensor does not register the temperature change when the exhaust recirculation valve opens.
How to fix or reset OBD-2 code P0401
When fixing error code P0401, people quite often just replace the exhaust gas recirculation valve. But after that, they get that OBD error back again. The exhaust gas recirculation valve is not always the culprit.
Some suggested steps for troubleshooting and correction:
- Use a vacuum pump, open the exhaust recirculation valve, monitoring the engine RPM and DPFE voltage. There should be a noticeable difference in RPM when the EGR is open.
- Clean the exhaust recirculation valve as well as the tubing to remove deposits.
- Check voltage at DPFE, compare with specified values in your specific model’s repair manual.
- Replace the DPFE sensor.
- Replace the exhaust recirculation valve.
Diagnose and repair of problems
First you need to read all saved data and error codes with the scanner. Then clear the error codes and test drive the vehicle. To find out if error P0401 appears again.
Check the vacuum lines, wires and connectors going to the exhaust gas recirculation valve. Also check the control solenoid valve and the exhaust gas recirculation system temperature sensor.
After that, check the operation of the exhaust recirculation system valve. It is also worth checking the operation of the exhaust gas recirculation system temperature sensor. The temperature sensor should change when the exhaust gas recirculation valve is opened.
Then remove the valve and the exhaust gas recirculation temperature sensor. Check for excessive carbon buildup and clogging of the system ducts.
On which vehicles does this problem occur most frequently
Fault code P0401 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Acura
- Audi (A4, A6, Q7)
- BMW (X3, X5)
- Chevrolet (Aveo, Captiva, Cruze, Lacetti, Lanos, Spark)
- Chrysler (PT Cruiser, Sebring, Voyager)
- Citroen (C5, Jumper)
- Daewoo (Leganza, Nexia)
- Dodge (Caravan, Stratus)
- Fiat (Doblo, Ducato)
- Ford (Escape, Explorer, Focus, Maverick, Ranger, Taurus, Transit)
- Honda (Accord, CR-V, Civic, Jazz)
- Hyundai (Grand Starex, H1, Santa Fe, Sonata, Starex, Tucson)
- Isuzu
- Iveco (Daily)
- Jeep
- Kia (Sorento, Sportage)
- Land Rover
- Lexus
- Mazda (3, 6, Axela, BT-50, Demio, Familia, MPV, Tribute)
- Mercedes-Benz
- Mitsubishi (Eclipse, Galant, Montero, Outlander)
- Nissan
- Opel
- Peugeot (307, 406, 407, Boxer, Partner)
- Renault
- Saturn
- Skoda (Fabia, Octavia)
- Ssangyong (Actyon)
- Suzuki (Escudo, Grand Vitara, SX4, Swift)
- Toyota (Camry, Corolla, Fielder, RAV4, Tacoma)
- Volkswagen (Golf, Passat, Touareg, Touran, Transporter)
- UAZ (Patriot)
- VAZ
Fault code P0401 can sometimes be found with other errors. The most common are the following: P0088, P0244, P0299, P0307, P0400, P0402, P0403, P0404, P0405, P0406, P0407, P0408, P0409, P0420, P1359.
