The 12v + will always be there, you need a multi meter in between the 12v hot and the triggered injector ground. Set on dc volts. I still think you have a bad ground. W/o a good ecu ground the injectors won't fire.
I agree that it keeps pointing back to the VATS. But how common is it for a chip to suddenly turn VATS back on when it used to be programmed out and running fine? I think the bad ground might be more likely. However....I guess I wouldn't rule out spontaneous reprogramming, it is a Fiero after all . I did it the safe way. I have a frequency generator AND have it programmed out of my ECM.
Make sure there aren't any "loose" wires from the ECM. One of the grounds could have broken off.
1st - I am not sure a logic probe would pick up an injector pulse - use a volt meter and check it at the ECM to be sure you have the correct side. It should show a pulse during the initial startup, no way it would fire without the pulse (unless you are manually adding fuel).
Are we sure the VATS programmed out? This is exactly how it reacts to no VATS signal.
It could be that the PO located the bypass someplace else other then near the ECM. Is there a wire in the green ECM plug on pin F10? If so there still could be a bypass module someplace. I would trace that wire back and see where it goes. If not, then you can be sure that the VATS has been programmed out (unless the chip was changed for one of those Hyperchip thingys).
You can then go from there. If the engine is firing then I would say the injectors are working fine (the ECM is just turning them off is my guess - back to VATS). Like other said, check your grounds (I would even add a ground to the ECM case). Personally I would suspect a bad MEMCAL or ECM - ECM is easy enough to swap out, the MEMCAL would have to be flashed though to fit your car (VATS programmed out, etc).
[This message has been edited by Mickey_Moose (edited 06-18-2015).]
I think it's safe to say that your VATS originally was programmed out. Although it really does seem like you don't have any VATS bypass currently. You should contact Stickpony and get another chip, or install a bypass circuit.
Yes...except I don't know of any place you could go. I have my own burner, so I just sent files back and forth with Stickpony, then burnt my own chips. Maybe someone else knows a place that you could bring the car in your area.
Since there is no VATS wire it would have been programmed out.
That leaves me to believe bad MEMCAL (chip) or ECM.
All you can do is send the chip out to someone to verify the code (VATS is off) or have Stickpony send you another one. If you have someone in your area with a 4.9l you can ask them to test your ECM in their car, if it does the same thing, then install their chip.