P0401 OBD-II Trouble Code
If you wish to share this article, please link back to this page instead of copying-and-pasting this article elsewhere. Why?
Insufficient EGR Flow
What does that mean?
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
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)
- Replace the EGR valve
Related P0401 DTC Discussions
- 1998 Ford Taurus SE P0401 Code
I got into an accident about five months ago. I collided with another car at a low speed while turning left, and the only real outer damage was a broken right headlight and a dent in that area. But since then, I've been having issues with my check engine light. It started running a P0401 code shortl...
- p0401 code and strong gas smell
Hi guys... hope you can help unstump the dummy. 2000 Isuzu Rodeo v6 engine automatic.. for several weeks we can smell a very strong gas odor when the car is running even in the car following behind it ! Used a Snap-on solus reader and the only code I get is a P0401 which is a egr code. I don...
- 2002 Mitsubishi Montero Limited 3.5L P0401 and P0403
Both of these codes point to a problem with the EGR system. However, with both codes showing up, there has to be one solution. Anyone know what it is? Any ideas? 401 says insufficient flow. 403 says EGR solenoid. Is the solenoid bad or clogged and causing insufficient flow?...
- 1999 Toyota Camery P0401 Code
Getting this code. Anybody have suggestions or links on how to fix this problem? Will this YOU TUBE advice work for Toyota Camery? http://www.youtube.com/user/scottykilme ... gfT3kuY8lc...
- OBD-II P0401 - 1996 Ford 302 Bronco -
Can anybody tell me what this code means. On my code-key reader it read "exhaust". Thanks...
Need more help with a p0401 code?
If you still need help regarding the P0401 trouble code, please post your question in our FREE car repair forums.
NOTE: This information is presented for information purposes only. It is not intended as repair advice and we are not responsible for any actions you take on any vehicle. All information on this site is copyright protected. If you want to share this article or information with others, please link to this page, don't copy and paste it elsewhere.