I was heading back down from Warrington today and driving along the A1 south bound. I accelerated from 60 to 70 in 6th gear to pull out and pass a vehicle and I felt a loss of power. I drove a bit further and it felt like the turbocharger was not working, so I pulled in at a side road and checked my car with the STS unit. It bought up a fault code of P0234. I know that is an over boost condition but it has never happened before. I did nothing out of the ordinary and I wasn't putting my foot down! I reset the DTC and drove the car and it felt fine again.

I have checked the exhaust for any white or blue smoke and it is clear. There are no air leaks from the pipes that I can hear? What could have caused this to happen suddenly? Any ideas?

I got this after fitting the decat, it happend in sixth too but has never returned. I presume in my case it was due to the lack of restrictions in the exhaust meaning quicker spool up, the code /limp has only appeared once. Yours may just be close to the the Ecu boost limit on the map or maybe a boost leak?

Today I rechecked the car with the STS unit and it bought back the old P0299 lower boost limit reached fault code.

So I jacked the car up and checked all the boost hoses and vac pipes. I could not see any obvious sign of a tears or splits in any of the hoses or van pipes. The only thing I did find was some dirt around one of the seals in the boost hoses. I have since cleaned it and put it back together. I took it out for spin and it felt better and was more responsive. But again it bought back the P0299 fault. After having trouble free running with no fault codes to getting two codes that are opposite to each other. One over boost and one under boost. I am going to change the N75 valve and see if that works? Its only £20 but it look a right p.i.a to fit

Did you ever get to the bottom of this?

I have experienced this twice now. Driving along normally and all of a sudden go to accelerate and it feels as though the turbo isn't providing any boost.

No warning lights illuminate and there are no rev limits etc so it's not a proper limp home mode. Switch ignition off then on again and it's fine.

I have checked with a generic fault code reader but there were no codes - It was a few starts since the issue though so may have been automatically cleared?

I'm assuming you've got a Shark remap if you're using an STS?

Any comments Shark/Ben?

I changed the N75 valve and have had no issues since....famous last words! Watch this space lol