Join Date: May 2011
Location: Lehi, Utah
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6.0 low power code p123b & p0401 (Have autoenginuity)
I have a 2004 F-450 that has been nothing but trouble the last few years. The current issue is code p0401 EGR and p123b turbo. The truck is gutless below 3000 RPM and not great above 3000. It takes forever for the truck to reach 3000 RPM. We use it for towing and tow quite a heavy load every day. The EGR was deleted last year by a local shop. I'm not sure if that leads to permanent p0401 or not. When they did the delete I asked them to service the turbo since they had to have it off anyway and it seemed like the boost was a little low back then. I don't know if they actually serviced it or not. I ended up with a high pressure oil leak as well so the truck was in and out of the shop three times before they found the braided line that was the issue. I am not the one that drives this truck, but I own it. The guys that drive it aren't super mechanically inclined so they don't always give good answers when I ask them things. They normally drive from job to job and stay at a job for at least an hour or more so the truck never gets super warm. They have said that if they have job that is really far away it appears that the problem goes away a little if the truck has run for quite a while. I took a half day off work today in the hopes that I could solve the problem between this afternoon and Saturday. The truck needs to go back in service and I have to work on Monday.
After picking up the truck just now and connecting my Autoenginuity I see that BARO pressure is about 12.9 (I live about 4500' elevation) and MAP was exactly the same at KOEO. At idle MAP is slightly higher than BARO, maybe 1 PSI tops. When I drive it MAP has a hard time getting above 20 PSI until I'm at about 3000 RPM then it will top out at 29 PSI floored once I'm over 3000 RPM. Is boost pressure the difference between MAP and BARO? If so, that means I'm topping out at about 16 PSI of boost. Getting on a downhill freeway on ramp I floored it the whole way and never exceeded 29 PSI MAP. For fun I tried actuating the VGT solenoid and it would hardly run at all. Meaning I clicked VGT solenoid command open in the AE software. When I did that I was going down the road with it floored and the truck would not exceed 3000 RPM at all. I unclicked it and the turbo kicked in immediately making me thing the VGT solenoid is working.
Reading through other treads I see you should check the MAP hose, which looks good but I haven't removed it yet. Also check the EBP valve for gunk. I am not sure if the truck has been flashed to infer EBP or not. It has been serviced at a dealer after the update was released. I thought I read somewhere that the p123b code was unique to the update? Not sure about that. I have yet to examine the EBP, but I will after I post. There is an exhaust leak, not sure if it is large enough to cause such a problem. Looking in the passenger wheel well I can see 1 bolt missing from the exhaust manifold. I'm sure this isn't helping the problem, possibly it is the whole problem? I sort of hope not I've seen posts about how awful the manifolds are to get off. I appreciate any and all input.
If it is just the manifold is it easiest just to grind off stubborn bolts and replace them? Should you get a gasket once the manifold is off?