I've searched and read all threads mentioning P0028/P0026 here. There's seems to be only a handful of common causes for these codes. Here's my experience so far.

I've owned an '07 LR3 HSE with 156k mi for a little over 1 year. Maintenance records show it has been well maintained its whole life. it's my daily driver and sees occasional off-roading up here in the mountains of Colorado. I recently got a P0028-77 code by itself. No work has been done to timing components, and if I clear the code after the oil is hot, it does not come back until the next cold start (i.e., after sitting overnight). There is no noticeable performance or fuel efficiency loss (18.5mpg).

I've done the following:

• Cleaned VVT electrical connector and leads (they were a bit oily, presumably from when the VVT gasket failed last month - since been replaced)
• Flushed engine with BG109 EPR, followed by oil change and new filter (Shell Rotella Gas Truck 5w30, NAPA Gold filter, same as previous OCI)

So I can only assume there's an oil blockage somewhere, likely either in the solenoid mounting bracket or solenoid itself. So i guess next steps are to open up the LH valve cover and front engine cover to:

• check/replace seals on the solenoid bracket
• check/replace VVT solenoid

Questions:

• Do I have to remove the front engine cover to replace the solenoid, or can that be accessed by only removing the valve cover?
• Where can the solenoid bracket seals be sourced? Should I just measure the old ones and find some suitable high temp, oil compatible replacements?

Any insights or thoughts? Thanks!