igf

[totta crolla]

Whilst l know (or thought l knew) what igf does l wondered if anyone knows what it actually monitors as a return to the ecu?
I'm chasing a 0° btdc timing issue on a Freedom ecu and when this happens the engine will not start.
The display shows 0° btdc in the ign timing log.
I did nothing but cleaned some fouled plugs and the timing is back to 18° btdc and the engine starts.
lt looks as if igf monitors the actual spark at the plug rather than assuming the signal has been sent so the plug must have fired. (which was my understanding)

Update..
some people will already know this but a little testing proved that fouled plugs in themselves may not be the only reason your 4age won't start.
It turns out that no igf return due to a lack of actual spark at the plug will cause a zero ignition command and also a zero injection command, this of course makes perfect sense but it's nice to know what's happening and this might be useful for someone sometime.

[Davegt27]

from Google

IGF (Ignition Confirmation Signal)
The ECM uses the IGF signal to confirm each ignition coil has fired after it sends an IGT pulse. The ECM supplies a 5V reference voltage on the IGF circuit shared by all coils. Each time a coil fires, its igniter pulls the IGF 5V reference voltage to ground.