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Discussion Starter · #1 ·
Hey everyone, haven't posted on here in years and hope everyone's well. Had the TTS for just under 5 years, it's finally all paid off and I'm still loving it! Haven't really had any issues crop up except this one and it was an easy fix, so hoping this will help someone out there!

A few weeks ago the TTS started to have this weird bucking/shuddering/hesitation on light acceleration. It was only when the car was hot (oil temp high), usually if I stopped for a bit and then launched lightly just under boost. It really felt like the clutches or mechatronics might have been giving out and I started to get really worried, but then I realized it was actually happened in all gears under the right throttle input, even top gear cruising, going from coasting to light acceleration.

I scanned the car with VCDS and got the following:

1 Fault Found:
15211 - Oil Pressure Regulating Valve
P164E 00 [047] - Electrical Malfunction
Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 254
Mileage: 92651 km
Date: 2021.07.24
Time: 13:42:08

I'd actually gotten this code last July as you seen in the log, but it only happened once and I figured it was a fluke and cleared it. After seeing this, I did an Output Test on the N428 Oil Pressure Regulating Valve, and it was completely dead, nothing at all. If you're curious what this valve does, read Page 17 of this:

Basically the valve switches the oil system from about 24 PSI under 3500 RPM to about 50 PSI above 3500 RPM. When it fails, it fails to the high pressure state so it had been on high pressure all the time for god knows how long, and never turned on a single light or error! I ordered a new valve for about $100 USD, but while waiting for it I wasn't sure how could this could be causing a drivability issue, and thought for sure something else was going on. But then I remembered the variable valve timing cam phasers are actuated off the oil supply. I drove the car around the block a few times while recording a bunch of different data, but most importantly camshaft adjuster commanded position vs actual for both intake and exhaust, and sure enough, my exhaust camshaft was going all over while my intake was just fine:
Rectangle Slope Line Font Parallel

Trust me you could feel all the grey squiggles and it drove like crap. Got a replacement N428 valve (06K115243L) in the mail and popped it in. Literally couldn't be easier to access. Take the bottom engine cover off, and it's right above the oil pan by the lower accessory belt. You loosen a single screw, undo the connector, pull the belt down and out of the way (quite firmly), twist and pull the old one out, pop the new one in, and screw in and connect.
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Auto part Drinkware Gas Chemical compound Cylinder

New one sounded like normal when I ran an output test on it, and car is happy and doesn't throw any more codes. Most importantly, it drives like normal, and when I took camshaft data with the new valve and the oil system in the correct, low pressure mode, it looks smooth and great!

So lesson is, these fail, they're cheap and take 5 minutes to replace, and they can completely (and temporarily) mess up the VVT control loop and refinement of the drive while not turning on any lights.
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