Cybaster

Hi all
So I am trying to get my S5 TII started again and I have hit a wall.

I am mainly following this previous thread for reference in diagnosing my car:
https://www.rx7club.com/2nd-generati...e-help-700242/

I managed to redo all the grounds properly and follow the steps outlined in the thread above.


With the AFM unplugged I am able to see a ref voltage of 5v on the BR/W wire on Boost Sensor, OMP, TPS, I am getting spark and injector pulse.
With the AFM unplugged I see check engine light and code when I jumper the test connector

With the AFM plugged in, the ref voltage drops to 0 and the car does not crank over (tach does not blip when cranking), no spark at the spark plugs.
Also with the AFM plugged in, the check engine light is off even if I jumper the test connector.

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what I've tried:
- 2 AFM, one original one that came with my car, another I recently purchased "known good" N370 AFM. Also verified with the FSM that the latter is within spec.
- tried with two different N370 ECUs both "known good".
- verified BR/W is getting 5v when unplugged
- verified BR/B has continuity with chassis ground and ECU ground

I'm kinda stuck as to what else it could be. so any help or advise is appreciated. if there are any electrical gurus in the Northern California area, I would love to buy you a 24 pack of beer and beg that we figure it out together.