Would a bigger muffler cause a P0401 CEL?

I can't seem to figure out exactly what is causing the P0401 CEL, last mechanic I spoke to claimed it is b/c of the bigger muffler not enough exhaust gas is recirculating. Does this make sense? Thanks for any input guys, CELs drive me crazy!

 

Wow if your sure of your code time for a different mechanic.

Although I could be wrong here and you have a emission system I have never seen or heard about.

Where Exhaust gas is taken from behind the muffler and rerouted back into the engine.

Could be something as simple as a Vacuum hose or filter or sensor.

Depending just what your working on.

 

Yea, he was explaining to me that since my muffler is bigger than the factory one that I had that it is not creating enough back pressure to properly recirculate and creating an insufficient EGR flow. I have a 1999 Tacoma 2.4L so no crazy emission system, just a bigger muffler I had installed for sound.

 

P0401 - 'insufficient EGR flow'
Never heard of a muffler causing this. Seems to me that the engine vacuum is pulling the exhaust into the intake. I had this code in my 2.7 motor, and cured it by removing the EGR temp sensor, scraping/cleaning off the built-up crud, and re-installing it. After clearing the code, it never came back. This could also be caused by a faulty EGR modulator, leaking air hose in the EGR system.

 

Already changed the EGR modulator and the temp sensor so they are fine. I guess I will do the vacuum lines next. I also saw something that the VSV for the EGR could also be the issue

 

I would probably investigate more in the area (egr) that the code specifies. On my '97 2.7 the cat is gutted and has an imco(knock off flowmaster) so flow is not gonna get much better and I've never had an egr code and actually only occasionally get the o2 sensor code which is expected with a gutted cat.

 

Your catalytic creates all the needed backpressure for the EGR to function. If you have a good enough scanner available, such as a newer Snap-on or Autologic, it will not only tell you the EGR actuations, but as well the fuel trim and temp changes when this happens.

Though in any case, this error is most likely caused by a bad vacuum line or actuator. I'm not that familiar with the EGR systems on this engine, but as you already ruled out the temp sensor, I would check out the vacuum actuator for the valve and any lines involved. The other possibility would be a burnt or clogged EGR passage.

Time to fix it yourself then find a competent mechanic.

 

Thanks guys, I will try to fix it myself. I did install a flowmaster cat ($100 on Amazon) since the original was done, not sure if this will cause any issues with the EGR backpressure. I will be starting with the easiest and cheapest first, the vacuum lines, then go from there. Thanks again!

 

Your manifold vacuum has more to do with EGR flow than your exhaust pressure, not to say that running a track pipe would not have some effect on it. Even a high flow cat is going to create pressure.

 

Download the repair manual. It clearly shows how to test each part of the EGR system (VSV, modulator, EGR valve, etc.). There's no need to replace random parts and hope they fix it. Other than a part that doesn't work, you could have a clogged passageway.