Hi all,

I was handed down my 300D about two years ago, and it ran (more or less) perfect. Stuff broke, I fixed it (usually by reading posts from here, thanks guys), but now I've run into something I can't wrap my head around. As usual, its a boost issue. I've got ~3 PSI at the test RPM/WOT.

I'm 90% sure my lack of boost is from the vacuum transducer for the wastegate (Y31, if you've got the FSM) not working. When the engine is on, there is no voltage across the plugs, and no vacuum on the line going to the wastegate. However, the transducer itself isn't the problem, because run from an external power source it works fine, boost is good, and all is happy.

(From here on, I'm confused as can be)

From looking at wiring diagrams, it looks like this ground is supplied by the manifold pressure sensor (S66) but also goes through the alda's overboost protection solenoid (Y30). I'm pretty sure the sensor is broken (some guidance on how to test it would be great), but connecting the battery's ground to the sensor doesn't fix anything.

I can supply pictures if needed, and thanks in advance.

tl;dr: wastegate vacuum transducer (Y31) isn't receiving power, what do I do?