1.8TSI down on power - P0299 fault

Hi all,

I have a 1.8TSI which intermittently is down on power.

I'm getting P0299 - 000 - Control Range Not Reached - Intermittent according to VCDS, so I've checked the following:

1. Diverter valve - was the newer piston type already, but I replaced it regardless. No change.
2. Checked for boost leaks.
3. Cleaned MAF and ITG air filter (the latter was minging, and had been over-oiled by the previous owner - hence the MAF clean too).
4. Checked it's not possible to blow from PCV inlet manifold hose into PCV system.

I'm not getting any oil around the rocker cover/oil filler cap, which I believe would indicate PCV failure - but there is oil around the top timing chain cover area.

Are there any other things to check?

Thanks,

Andy