I cant believe that this hasnt been posted, and it probably has, but I cannot find it anywhere. My question is simple, what signal causes an injector pulse? The reason I need to know is because my AIC is being tempramental and not working sometimes. It seemed like a bad ground, but Ive regrounded a million times. I get 12v at both prongs on the injector connector. I figured that one of those 12v must become a ground in order for the injector to open, but I just need to know for sure so I can continue testing the aic and trying to find the problem.
Thanks,
Chris

 

From looking at the FSM, pins 3F, 3C, 3H, and 3E on the stock ECU are the signals to the 4 injectors. (page 50-22 in the FSM). I don't have a diagram to show what pins those are. Are you trying to piggy back the signal to the AIC off of the stock wire harness?

Hey, where did you get your TO4b? Pm me.

 

Typically +12VDC is constant on. The actually fuel injector signal is a ground square wave. It's a "pull down" or "pull to ground" signal.


-Ted

 

so let me get this straight for sure. the 12v is constant, but there is a 12v to ground wave and the different frequency is what allows the injector to control the pulswidth time....right? So I should test both leads coming out of the aic and see that one of them has a pulsing ground? Thanks

 

Yep, you got the theory right.

I doubt your DMM would "see" the pulse. An analog meter might be able to show it, but most "cheapie" DMM's will not show the pulses accurately. You really need an o-scope to show those pulses - got one handy?


-Ted

 

Or a test light in case you don't have a scope lying around

 

the engine computer is the end all decision maker on the ground side but remember there is a power side and subsystems which tell the computer there is an engine running/rpm/ ignition system signal as well.