000665 - Boost Pressure Regulation: Control Range Not Reached

[SebRogers]

I've had my 170pd for about 7 weeks now and I basically love it. But I'm having ongoing problems with intermittent limp mode...

Within 300 miles of taking delivery it went into limp mode twice. I popped it into my local indie who read the fault codes. Long story short (I forget the actual code) it was overboosting. The diagnosis was sticky turbo vanes. I wasn't ecstatic about fitting a new turbo but my indie's always been 100% reliable before, the seller agreed to pay a small contribution (gratefully received) and the car was a good price to begin with, so I went ahead.

New turbo fitted, all well for a few weeks. Until today

The car's booked back in with the indie in about a week (the earliest they had a slot), so in the meantime I popped it down to my local non-specialist garage, where they very kindly did a code read. It was this:

000665 - Boost Pressure Regulation: Control Range Not Reached
P0299 - 006 - Short to Plus - Intermittent

Plus some freeze frame details, which I don't have.

It's a different code to the previous one - not sure if that's good news or not. As far as I understand it, this code's unlikely to be caused by the turbo itself. And the circumstances are slightly different.

Pre-new turbo, limp mode would coincide exactly with the loss of power. This time around I was trying to accelerate from around 50mph in 4th (c.2200rpm) up a slight hill. Feeding the throttle in, there was nothing. So I planted my foot. Nothing, for about 3 seconds. It just wasn't pulling at all. And then it went into limp mode and I started losing speed...

Boost leak? Something else? Pointers gratefully accepted. I'm sure the guys at my local indie will get to the bottom of it, but in the meantime it'd be good to have some idea of what kind of bill I'm facing!

[Crasher]

There are three main possibilities, the new turbo is faulty, the Air Mass Meter is faulty or the Thrust (MAP) sensor is over reading. You need someone to do some Group 011 zone 2 and 3 boost logs and see if zone 3 is spiking significantly over zone 2. Also the operation of the actuator sound be checked and the integrity of the vacuum system to check for any leaks. The VAG system VAS PC says that fault code means the turbo is defective. That fault code does concern me though, the short to positive part. Which diagnostic system was used to read the codes?

[SebRogers]

Thanks Crasher. Faulty turbo hadn't occurred to me...

Don't know which diagnostic system was used, to be honest. It's my local garage, they service everything, I'm a good customer and they were really only doing me a favour running a check on the spot. I think it was VCDS but I could be wrong. The indie that I use is a (fair) bit further away and they can't accommodate me until next Friday, so I probably won't know more until then.

Does 'control range not reached' mean it's underboosting?

[Crasher]

Yes it is under-boost so forget my spiking ramblings, I was exhausted last night after two hours in the gym.

[SebRogers]

Thanks again Crasher. So... still faulty turbo, AMM or over-reading MAP most likely candidates? The last two I can understand leading to underboost but in what way could a turbo fault lead to underboost?

Will check vacuum system for leaks too...