Join Date: Oct 2010
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Do you have a scan tool such as autoenginuity. If you don't, I know you don't want to hear it, but you will probably pay for it with this fix alone.
I have had some of these problems. First, the P0046 code could cause a lot of these other codes. The 0046 will probably lead you to the vgt solenoid. That thing rarel, rarely, rarely goes bad. So, with the engine running at idle unplug the vgt solenoid a few times and see if you can hear the turbo operating. Normally at idle you will hear the exhaust "hissing" because it has the vanes moved to a minimum so that the exhaust velocity increases as it hits the turbine wheel. When you unplug the vgt the vanes should open up and the velocity is decreased and the "hissing" will go away. Sometimes you can even hear a little "whoosh" at the intake of the turbo when the turbo starts to spin down when you uplug it.
If you are not getting any change when you unplug it, I would look through the wiring for a fault/short. I had one that would work at idle, but when I got torque on the engine it moved a little and caused a short. Took me forever to realize it was a short and it ended up being all the way down into the main part of the harness as I cut open the corregated protection tubing and followed the wires until I found them shorted together due to chafing against each other.
If that turbo is not working correctly you can get low back pressure compared to what is being commanded or you can get very high back pressure.
Also, there is tube that runs from the MAP sensor to the intake manifold. Those are prone to getting old and brittle and they can crack and if they are leaking they screw everything up. Even if it is not cracked, take it off of the manifold and clean out the brass nipple that it goes on. Sometimes Carbon plugs that thing up.
Start with all of that. Again, if you had a scanner you could actually see what the baro and MAP are giving you as well as EBP. The vgt solenoid has no feedback system, but you can see what the duty cycle is supposed to be at any given time.