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# What are the causes of a P0401 error code?
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
* Carbon buildup in the intake manifold
* Carbon buildup to the EGR temperature sensor
* Defective EGR temperature sensor
I get this error every 2-3 years.
All I do is clean out the EGR valve and Plenum on my 98 Honda 3.0.. reset the code and it’s good for another few years. I have never replaced my EGR valve.
Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
# What are the causes of a P0401 error code? 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 * Carbon buildup in the intake manifold * Carbon buildup to the EGR temperature sensor * Defective EGR temperature sensor
I get this error every 2-3 years. All I do is clean out the EGR valve and Plenum on my 98 Honda 3.0.. reset the code and it’s good for another few years. I have never replaced my EGR valve.
Take out your EGR valve and give it a good clean with some Carb/Throttle Body Cleaner.