Quote Originally Posted by LosMan603 View Post
Any luck with this? Curious to learn more about what you found out.
Well the MAF is at least getting +12V so theoretically it can work, I've narrowed it down to something like:

1) There is no +5V to the Throttle Position Sensor, in fact there doesn't seem to be +5V coming out of the ECU at all.
There is possibly a short to ground somewhere on that +5V line.

2) This means there's no +5V to the other sensors which run off 5V, so at least the MAP sensor and possibly others.

3) There doesn't seem to be any continuity from the TPS signal pin back to the ECU.

So basically when I open the throttle, the MAF seems to be telling the ECU, hey, here's a bunch of air coming in
But the ECU is like, why? The throttle is closed. And thus not giving the engine proportionally more fuel to match.

My next step is probably going to be pull out the whole Legacy loom (which I need to do anyway to put the Impreza loom in to run the headlights/indicators/power windows etc), cut out all the Legacy's cabin stuff until I'm left with a "standalone" engine loom, and then check continuity from every sensor plug to each corresponding pin on the ECU plug.