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We have a 6.7 with what we think is excessive back pressure at the turbo. Came in barely able to drive. Had stored codes P0471,P2262,P2563. Active code P1451. We've done all the checks we can think of. Had tech line tell us turbo was plugged. Replaced turbo & vacuumed out exhaust components. Started & ran ok Friday. Came in Monday and started up & problem was back. Doesn't rev over 1500 & sounds like exhaust plugged. Had codes P242F,P1451. Dropped exhaust at turbo, no change. If we disconnect EGR tube at EGR valve then it will rev higher. Checked EGR twice & is not stuck open. Tech line says to clean EGR valve. We are completely stumped at this point. Any ideas?

Without seeing this and running tests on it I may be a bit misleading. The tube for the pressure sensor may be plugged, I've run into this few times. More than that I've seen the electronic control for the pressure gate of the turbo screw up. Without backpressure the turbo may not spool up. The truck should still drive around with a failed turbo without any real top end though. Another issue may be fuel pressure. A trick I use is when I have someone revving it up and it's flat I spray WD40 into the air intake and see if it spools or powers up.

We cleaned EGR and have the same results. Our back pressure at idle varies between 50-80 inHg. This is with exhaust dropped at turbo. With egr tube disconnected its 32 inHg. We're not sure what back pressure should be. Will try wd40 to eliminate lean possibility.

Fixed problem. Turbo was stuck in full closed position. Replaced turbo. Runs great.

Thanks for posting fix.