Just put a bd turbo back exhaust on my new duelly only had about 800 miles on it when I installed it. 2 days later check engine light came on. Threw the tech2 on it (im a gm tech) three codes p0299-turbo underboost p0401 egr- p0404-egr. Before I go trying to fix a problem i may have created did anyone else have this result with exhaust install. called tac today, didnt tell them i had done exhaust they had a few cases on intercooler pipes being loose, it would pop all three codes that i have. This is a federal emissions truck. I allready loaded the newest calibration in it. thanks in advance.. John

You have the North east emmissions being that you are from NJ. It is basically the same as CA. The check engine light should come on with the mod you have done. However....not sure the underboost code should be there. The variable vane turbo, to my kowledge, does not work off of back pressure. So....I am thinking you might have something going on with the loose intercooler pipe. Somebody here will be able to help you with that more. Maybe post something in the ask the techs forum. Oh yeah...enjoy your new truck!http://www.dieselplace.com/forum/smileys/Big Smile.gif

I've got the EGR exhaust plugged off with the EGR electrical connector plugged in on my 4.5 LLY, and I have the p0401 and p0404 codes, (insufficient EGR flow), coming up on my OBDII scanner. Edited by: mac1234

didnt perform the egr mod yet but I did find a loose intercooler clamp causing the 299. anyone know the cure for the egr code I assume this junker works off backpressure. Just cant stand the light. thanks John

Well the trucks with the more sensitive EPA programming, i.e. CA and the NorthEast where you live, are setting codes and displaying SES lights with either the EGR unplugged or the CAT removed.


The primary reason the VVT turbo was installed was to create enough back pressure for the EGR to work, it also needs the CAT to create that pressure. So if you remove the CAT, you lose backpressure and get a few codes.


If you disconnect the EGR, you get a few codes and some have seen as many as four, and an SES light. The trucks with just the Federal emission package do not set an SES light, but are setting codes for insufficient EGR flow.


Seems like I've seen some folks post about disconnecting the EGR and not setting codes, but I can't swear to that. Check out Max Power's thread on disconnecting the EGR and even though it's long, you'll get a better idea of what's happening and the effort being made to disable the EGR without setting codes or the SES light.Edited by: Zeeb

On edit...I have codes with the egr disconected...no ses light though.Edited by: dpower

thanks. dpower do u think this loss of back pressure have a negative effect on turbo longevity. Im gonna put a juice/attitude on it not sure if i want to put the cat back on. but that ses light sux Thanks John

Hay guys I have a Calif. 05 truck and I put MBRP turbo back 4" exhaust on. I am getting codes like crazy. I even get the limp home code where my truck only goes about 65 mph. http://www.dieselplace.com/forum/smileys/Cry.gif What can I do. I also get the under boost code. Please help me.


Thanks guys.

I am not up on the codes yet nor have I fully explored the exhaust system, but I am familiar with that 65 mph problem you are discussing. It is called "soft limp mode", it happens when the PCM sees something that it feels isn't right and possibly damaging (too much boost at the wrong rpm for example) it then sets an rpm max of 2000

This rpm limit is enforced in every gear including park and neutral. The truck will perform fine up to 2000 game party over. Turns out that is 65mph in OD.

It is easy to clear though, next time it happens just pull off and kill the truck and wait 30 seconds and restart. The electronic leash will be gone and you will be back in business.

I learned this from calling Quad, I figured the stealth had caused the problem but it was me that did, I was cruising about 75 and was blipping the throttle for fun to make the turbo come in when my party was spoiled. Quad says the PCM will learn over time and the problem eventually goes away. I have never had it happen again on mine so I would say that assessment is correct.