Hey everyone,
I’m having a weird issue with my 2016 Volkswagen Passat TDI — the power suddenly drops while driving, and I keep getting code P029900: “Boost pressure regulation: control range not reached.”
Here’s what I’ve done and checked so far:
The diverter (bypass) valve seems to be working fine
Vacuum supply is good
Vacuum lines look intact, no visible cracks or leaks
I already replaced the boost control solenoid (N75-style valve), but the problem is still there
I did a vacuum test on the bypass valve — at first it builds vacuum properly on startup. But after a few presses on the gas pedal, the vacuum drops off completely after a few seconds, and the P029900 code comes back.
It feels like something is cutting vacuum control after a few seconds of running.
Any ideas what could be causing this? Could it be the vacuum pump? A leak I’m not seeing? ECU issue?
Appreciate any help!
