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Discussion Starter · #1 ·
Hauling cattle this afternoon running down I-75 South running about 70mph for some time my check engine light came on. Ran the scan gauge and found a code of PO401.
Truck ran fine but the check engine light stayed on, unloaded and came back to the house with no problems at all.
 

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Discussion Starter · #3 ·
cat back to stacks. No muffler

no programmers or EGR block
 

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ok any mods to aircleaner possibly k$n if so first thing to check after basics check maf connector egr connector if all connected remove maf sensor and clean with electric motor cleaner spray. and reinstall make sure air cleaner is clean. egr flow monitored through maf sensor signal. loose or blocked intake dirty maf sensor faulty egr can all cause this didnt see mileage on your post. check those first poss false code
 

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Discussion Starter · #5 ·
10285 miles on truck 432 hours. I am going to the dealer in the morning. Found out that PO401 is Inufficient EGR flow
 

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Yup. My guess would be it is related to your stacks and no muffler, but it's just a guess.
 

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Discussion Starter · #7 ·
That is most likely what the dealer will tell me also but I dont understand how or why the stacks/no muffler will do this now. I have put 3000 miles on the truck and hauling cattle daily since the stacks/no muffler was done back before Christmas.
 

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ok any mods to aircleaner possibly k$n if so
No K&N for the '06 yet.
That is most likely what the dealer will tell me also but I dont understand how or why the stacks/no muffler will do this now. I have put 3000 miles on the truck and hauling cattle daily since the stacks/no muffler was done back before Christmas.
The drop in backpressure creates a situation where the EGR "injects" less than the expected amount of exhaust into the intake.
This is going to be most likely to happen under high boost, which is when the exhaust has to fight the highest manifold pressures, and with a free flowing exhaust (especially without the cat) the EGR flow decreases. The EGR valve was designed to flow "x" amount at "y" boost and "z" RPM.

Time for a Fingers Stick and a blocker plate.
 

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Palmer,
I have a new LBZ and had exhaust put on mine with 1000 miles on it. I did not start having the P0401 code until 6500 miles later. Pacific Performance called me and they have the EGR code module ready and for sale on the LBZ. If your dealer tells you that the problem is with the exhaust and they will not do any work to it until you re-install the original exhaust then call up PPE and get that module. It is $150 and is easy to install. Their web site is www.pacificp.com. It is worth looking into. The module "tricks" the PCM into thinking that the EGR is working correctly and such will not set the check engine light. Just remember that the smell of cow S*it is the smell of money!!! I miss it bad but won't go back because of my kids!!
 
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