Hi,
My 2004 XC70 has been having a recurring turbo overboost code that occurs when I go above 4K RPM and drop back below 2K, but only at high speed and only when it's damp out. So far my solution to the problem for the past year has been to keep an OBD2 code reader in the glove box to get rid of the check engine light and bring the turbo back online, but I'm starting to think that perhaps I might want to consider a permanent solution.
My current theory is that the wastegate solenoid gets sticky when it's wet out, which is also supported by the wastegate solenoid error code that happens occasionally along with the turbo overboost error code.
Any suggestions?