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Service engine soon light with code P1404

Tiny
JALFANO24
  • MEMBER
  • 1999 BUICK REGAL
  • 3.8L
  • 6 CYL
  • TURBO
  • 2WD
  • AUTOMATIC
  • 90,400 MILES
My service engine light came on and when I had it checked with the diagnostic tool it came up with a P1404 error. See video.

I did take it to the mechanic and it was reported as being a air intake manifold leak that needed to be replaced, near the head gasket or something of that nature I don’t remember the exact wording. Either way it was costly with 3-4 hours of labor needed.

Could it just be the EGR valve as the video shows or can the P1404 message be caused by more than just replacing the valve?
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Monday, April 12th, 2021 AT 6:51 AM

9 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This code is pretty clear that the EGR is not in the position that it is being commanded to be in. However, it could be an electrical issue causing it to not respond so we need to run through the testing to prove it out. If you want to you can just replace it and retest as they are not too expensive but the testing is below if you want to run through it.

As for needing a manifold gasket, that can confuse the PCM and it will set some codes but this code is only there if there are no other codes related to it.

You may have an intake leak but I doubt it is causing this code. Please let us know why he thought that was causing this code. Did he perform this test and prove the EGR is okay?

Let us know and we can go from there. Thanks
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Tuesday, April 13th, 2021 AT 7:04 AM
Tiny
JALFANO24
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Thank you for the response. Unfortunately, I do not have the equipment to do extensive testing in the event it is an electrical failure. When I took it to the mechanic he explained what he did to confirm but honestly it was so a few months ago and I dont want to misrepresent his findings or how they came to that conclusion.

At this point I will bite the bullet and replace the EGR valve myself ($170 w/tax) and hopefully not cause any additional issues in the process.

Aside from the videos I found to replacing the EGR valve, admittedly seems easy, can you tell me what I dont know that I may need to do. For instance, should the battery positive be disconnected during this time or at any time during the process?

Should I be aware of anything else that needs resetting?

Will the service engine light go off by itself or should I run another diagnostic test to clear it?

I am not a mechanic by trade but I have replaced coolant elbows, fixed my supercharger by opening it and replacing the wheel inside, replaced the belts, alternator, and other easy accessible items so I am not afraid to work on the engine. But its what I dont know or what precautions I need to take that I have a fear of and making matters worse. Hope that makes sense. I even invested in a torque wrench just to be somewhat confident that bolts are tightened correctly.

Let me know your thoughts.
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Saturday, May 1st, 2021 AT 6:24 AM
Tiny
KASEKENNY
  • MECHANIC
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Totally understand. There is no resetting after replacing the EGR and to clear the code just do a battery disconnect for 10 minutes and that will clear the memory. If the light returns then the code is still active.

Please let us know if you need more info. Thanks for the update.
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Sunday, May 2nd, 2021 AT 5:51 PM
Tiny
JALFANO24
  • MEMBER
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Just to close this out. The EGR valve was replaced but did not resolve the issue. The recently replaced MAF sensor.
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Sunday, May 1st, 2022 AT 3:45 PM
Tiny
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Thanks for the follow up but if you don't mind me clarifying, the MAF sensor that was recently replaced was faulty and that was the issue?
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Sunday, May 1st, 2022 AT 6:12 PM
Tiny
JALFANO24
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  • 55 POSTS
Yes. See pic of wire. Since it was under warranty the mechanic got me a new one in exchange and once, I installed it all is well. Thoughts?
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Sunday, May 1st, 2022 AT 6:38 PM
Tiny
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Got it. More than likely the part they installed was either cheaply made or was a previously returned part that they just resold. Unfortunately, this happens pretty frequently.

However, for that to set this code is very odd. There clearly is no tie to the EGR position. This code was specific to the position of the EGR pintle so if this was not a coincidence then the only thing I can think is the MAF was not reading correctly causing some issue with the EGR.

However, even if the MAF was not reading correctly it would not cause the EGR to malfunction.

So, what I think happened is the MAF failed and caused the rough running, and this code was just an old code. However, if this was the only code there with the light on then I don't have an explanation.
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Sunday, May 1st, 2022 AT 6:59 PM
Tiny
JALFANO24
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Okay, so I do get that it could’ve been a faulty or bad MAF sensor and even if the EGR valve was a problem I’m glad I changed it. Strange that the code and the service engine light went out or was no longer showing after replacing the MAF sensor. Either way no major repair as was originally diagnosed. Now I just want to replace the spark plugs since it now has 98,000 miles.
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Sunday, May 1st, 2022 AT 7:11 PM
Tiny
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  • MECHANIC
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Agreed. Unfortunately, some of these things are not explainable just because we didn't have all the info that was going on. That is not your fault like you didn't supply something but just that something was happening that we didn't know.

I pride myself on always being able to understand what happened, but I care even more in "if it's not broke, don't fix it." So, this is not acting up so all is good.

Thanks for sticking with us and keeping us up to date. Please come back to 2CarPros next time.
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Monday, May 2nd, 2022 AT 6:31 PM

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