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Figuring out why your Check Engine Light is on means deciphering OBD-II (or “OBD2”) codes, and that can be kind of annoying. That’s why Car Bibles did it for you! You’re welcome, now let’s get into solving your issue.

OBD2 P0401: What It Means

This code is pretty straight forward: Insufficient exhaust gas re-circulation (EGR) flow.

There’s something up with the EGR system. It could be the EGR valve, the lines attached to it, the actuator solenoid, or the Differential Pressure Feedback Sensor, the DPFE that accompanies it. This system is used to re-circulate exhaust gases back into the engine to reduce nitrogen emissions.

Likely Symptoms 

Here’s what you may experience due to the P0401 code:

  • Minor Running Issues. It’s rare this will cause any running issue, if at all, so usually scanning the OBDII port and getting the code is how you’ll discover it.

Probable Causes

Here’s what could be causing the issue:

  • The DPFE sensor or EGR valve are broken and need replacing. These are integral to the system.
  • The EGR valve might not be getting enough vacuum to open and close. The little fella can’t do its job.
  • The EGR tube might be broken, bent, dented, or blocked. The tube that’s the pipeline to deliver these precious gases is blocked, faulty, whatever!

What Part Is Potentially Affected?

Essentially everything associated with the system. We should note: Replacement parts should be of OEM quality, as we’ve heard of cheaper/bargain-price DPFE sensors not relaying the proper signal to the PCM.

Possible Fixes

Here are the most common fixes to remedy P0401 code:

  • Inspect the EGR tube and all associated lines, especially the vacuum lines, replace if necessary. Spraying some carb cleaner in the EGR tube is one way to tell if it’s broken or blocked, as well as un-blocking it. Checking all lines for leaks is also a good first step.
  • Clean the EGR valve. Clean out the EGR valve as it might have deposits that are hindering its operation.
  • Use a multimeter to check to see if the EGR valve and DPFE have proper voltage. If each part’s values don’t jibe with what’s in your service manual, you’ll see that you have a problem.
  • Replace the EGR valve and DPFE. Sometimes these parts are cheap, especially the DPFE. Some folks just replace them both without using a multimeter and call it a day. However, EGR valves can be pricy, especially on modern cars.

Finding The Parts You Need

Now that you’ve figured out what’s wrong with your hooptie, let’s talk about where you’re gonna find that part’s replacement.

There are plenty of places you can buy auto parts from, but Car Bibles gets paid if you click this Advance Auto link so that’s the one we’re serving up. Advance Auto Parts also has delivery, curbside pickup, and a host of helpful diagrams to aid your repair!

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