2011 S60- Intermittent limp mode
 

Hi all own a 2011 S60 Twin turbo D5.
For the past 3 months I have an intermittent fault.

Under boost- normally higher in the rev range the car goes into limp mode.

Only fault code is p029900 - Turbo underboost.

The car drive for 10 miles and be fine all the way too work. Other times it is awful - almost continually flat.

I am actually in the trade. Smoke tested the vehicle, cannot see any vac leaks at all. Put some turbo cleaner through the system and it improved it for a week and then got worse.

Any ideas?
Jim

Could be exhaust sensor there is 2 of the just after the manifold screw them out if covered in soot replace do the one closest to engine first the cost round £60 each

t-map sensor