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Old 09-10-2021, 10:28 AM
Join Date: Sep 2021
Location: Minnesota
Posts: 2
B.Reilly01 is on a distinguished road
Trouble with pressure converter, small turbo overpressure, large turbo underpressure

I've had a problem with very occasionally popping an underboost code under heavy acceleration, and the local BMW dealer diagnosed it as a leaky pressure converter. So I went ahead and replaced the pressure converter and other vacuum solenoid. Now I'm popping codes for both overboost (small turbo) and underboost (large turbo). I've checked all the vacuum lines, and they are good. I think my pressure converter is bad (defective), as the actuator pulls back smoothly on startup, but never moves as boost builds (it's always directing flow to the small turbo). I have Protool on my phone, and it shows a changing duty cycle for the pressure converter, but it's not moving the actuator. With the car off, and a mighty vac attached to the vacuum supply side of the solenoid, I can pull vacuum and it moves the actuator (the solenoid appears to be normally open).

Should this be normally open or should it hold against the supply vacuum?

Thank you
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Old 09-13-2021, 02:36 PM
Join Date: Sep 2021
Location: Minnesota
Posts: 2
B.Reilly01 is on a distinguished road
To answer my own question, the pressure converter is normally open. When energized, it bleeds off vacuum through one of the caps. This was a case of a defective pressure converter that did nothing when energized.
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