HELP: power transistors and coil on plug ignitions

how does a power transistor work. i know that it amplifies the signal from the ecu to the coilpacks, but how? I am working on a car and it will not spark. I havent yet checked tha CAS, but the ecu threw an ignition code but not a CAS code. What kind of an ignition signal does the ecu output before the transistor? Anyone?

the power transistor is just like a solid state relay. It takes a small signal from the ECU to trigger a “switch” and then the transistor allows power to flow in this case it goes to the coils and provides power for the primary side of the coil.




but there is an ecu signal in, signal out and ground. does it act on the ground side of the coil. because i have power at the coil. i have ground at the coil. but when i put a test light on the signal wire, i get nothing. they tell me to do this in the manual, but i dont see where the power would come from, beacuse there really isnt any power coming into the ptu…

maybe i could use your logic probe to check it vs the FSM, but i ran the test with a test light and battery and it didnt match, but neither did the replacement ptu that i tried… unless they are both bad…

do you have a 300zx? because i have the same problem with a 90 300zx, i order the power tranisitor unit and hopefully it will help. I was also told at the dealership that about 7 years ago they replaced a shitload of these units. mine is going in tomorow and ill let u know if it helps. I am having trouble on cylinder 4, i tested all others by plugging a spark plug into the end and groundng it on the motor and i got spark on it with another cylinder’s plug, if its not the ptu then its gotta be the ecu or a short in the wire i think, i guess ill ffind out tomorow.

No you know what you are right i forgot there is power to the coils at all time on those engines. the transistor then completes the ckt for each individual coil.