Check engine light stays on the code that keeps coming up is P0401 changed egr valve clened out carbon build up also smell gas when first start not driving and fuel millage not as good car runs good though no misses idles smooth

In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit. Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open Clean out the EGR valve and/or tubing to remove deposits Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model) Replace the DPFE sensor (with a good quality / OEM one)

Read more at: https://www.obd-codes.com/p0401
Copyright OBD-Codes.com

OBD-II Trouble Code P0401 - Insufficient EGR Flow

EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR. You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms.

A code P0401 most likely means one or more of the following has happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum

Check it and keep us updated. Hope this helps (remember to rating this free answer).

Its either a faulty EGR valve or it has carbon build up inside.Take valve off and clean carbon out using a non-chrlonated brake cleaner and wire brush.

Are you reset the stored codes there? The EGR (Exhaust Gas Recirculation) valve controls an engine's emission of smog-causing nitrous oxides, or NOx. Its job is to route a portion of the exhaust gases back into the intake manifold. That lowers combustion temperature to below 2,500 degrees Fahrenheit - the temperature at which NOx gases form.

EGR flow is controlled by the engine's computer, which opens or closes the valve as needed. The EGR system is, for the most part, in the "out of sight, out of mind" category, and typical doesn't require regular maintenance. But if it gets clogged with carbon deposits, you'll see your "check engine" light come on, and a code (perhaps P0401 or P0402 or P0403) will show that there is insufficient flow. That typically results from a vehicle being driven persistently on short trips that don't allow the engine to fully warm up. Flow problems also can be caused by carbon buildup due to failure to change the oil frequently enough.

A clogged EGR valve not only results in higher emissions, it can affect fuel economy and cause rough idling - even serious engine damage. Valves can usually be cleaned, but replacement is often recommended.

About thie generic fault code, I suggtes check this description and tips for solution information: DTC-P0401-Tests (keep in midn that this code applied for alot brands, Hyundai included).

Keep us updated.

1. po401 refers to an insuffient flow of EGR gasses
2. locate egr valve
3. with engine running at idle
4. on the underside of the valve you can access the diaphram.
5. wearing glove if ness
6. lift diaphram while idling
7. does engine stall or run very rough?
8. if not remove valve
9. start engine
10. you should hear a very large vaccum leak and exhaust noise
11. if either are missing investigate cause
12. if ok reassemble.
13. locate DPFE sensor
14. inspect sensor for damage
15. inspect hose to sensor for damage
16. replace sensor

P0401: Isufficient Flow Detected in EGR system.
-clean the EGR port with the carburetor cleaner.
-clean the EGR passage inside the EGR valve with the caburetor cleaner.
Reset the light, if the light still coming back, then replace the EGR valve.

I had an OBD II 401 code and fixed it by cleaning out the EGR vacuum line in the intake manifold. I removed teh EGR Valve and the set screw below it. i used a rifle cleaning brush and one length of the rod. Then I replaced teh set screw. I started teh engind and let the vacuum **** some carb cleaner through the front port hole. when it was sucking good I replaced teh EGR valve and reset the codes. That fixed it.

When you replaced the EGR valve did you check the EGR passage to make sure it wasn't clogged. Since exhaust gasses flow through the EGR passage carbon builds up on the walls restricting flow which can eventually lead to the code p0401 Insufficient EGR flow.

check the metal line that comes off the exhaust and make sure it isnt plugged with carbon. also remove the egr and check the port and see it's clogged as well

Remove the EGR valve and clean it out. It's probably carboned up really bad constricting the exhaust flow. Also remove the EGR tubes and clean them out as well. I use brake cleaner and keep spraying the pieces out until it's pretty clean and re-assemble.