XC70: Engine Underboost P029900

[Imakora]

Hi All,

I've just finished replacing the cylinder head on my 2011 XC70. As a non mechanic, it''s been quite an education. Luckily I've had the use of another car, so haven't had a deadline. All seemed well, but I was getting an underboost error message. I couldn't find any leaks and tried testing the wastegate actuator using a vacuum pump as per Vida's instructions. These state that the actuator should operate between 4-8 cmHg and the actuator rod will move from right to left, retracting into the actuator. This resulted in no movement at all, so I immediately thought I'd found the problem. Fast forward a day and a bit and I've removed the the exhaust manifold and associated turbochargers. Removing the low pressure turbo actuator, I find the wastegate functions normally and that the actuator's resting position is retracted. This suggests that it requires positive pressure to actuate and contradicts the Vida function test.

Any help and suggestions would be much appreciated.

I forgot to add that I did find a crack in the charge air pipe. See attached photo.

[Imakora]

Just in case anyone finds themselves as confused as I was, the actuator requires positive pressure, not a vaccuum to operate. I'm unsure why VIDA suggests otherwise.

I've repaired the crack in the charge air pipe and hope that this solves the problem once I've reassembled the components.