[DirtySouth86]

Originally Posted by osudoc11

Chapter One: The first chapter.

So I had P0018 pop up just after installing a header, had the battery disconnected during the several hour install. Reset the ecu several times which would fix it for 2 drive cycles then it would pop up again. Took it to the dealer who told me problem must be with the header. I pretty much said that was bull. After taking it in several times they finally agreed to run diagnostics on it and told me I would have to pay a fee if they couldn't find the issue. Feeling confident I knew what was going on I said ok. They came back and showed the the ECU VVT Learn values were out of range and could not be "unlearned". This fits with the cam phaser problem. They replaced the cam phaser and the ECU. Problem fixed.

Chapter 2: What is causing this?

Now do I think something happened from putting the header on that caused the failure? No. Plus I was not driving it hard on the way home because it was basically straight piped and WAAYYY TOO LOUD. When they told be what was wrong with the cam phaser they said a part came loose on the back and was rolling around in there. If you search the other threads there are pictures of this.

From my research, which it is really hard to find actual answers or diagrams of this part, I think this is something related to a "detent valve". Our engines use a newish borgwarner cam phaser with mid position lock. Prior to this, cam phasers would have to figure out if they were going to advance or retard all the time, even at start up with no oil pressure. However, with mid position lock they can lock at 0 when not engaged, like at startup.

I think there is a mechanical failure going on with this detent valve and not allowing mid position lock to engage. When I still had the code on I did a lot of data logging. Sometimes the affected came would swing to its full retarded position while the good cam would go to 0. Its not a big deal initially. However, if you reset your ECU, the ecu has to calibrate the VVT system which I believe it does with mid position lock engaged. Since one side cannot lock at 0 it gets out of wack and is broken forever. So I think the mechanical failure had already happened at some point before the code happened. But when the ecu was reset it could no longer calibrate the vvt system until the cam phaser and ecu had been replaced.

Just my two cents on the issue. If anyone has any input or noticed something I said wrong, let me know.

I think you are definitely on the right track. The one we just repaired had that problem with the cam gear / phaser.