Quote Originally Posted by kur4o View Post
Hi Tom,

Did you managed to reverse the hardware side of ignition control. I am only interested in the signal that pcm sends to ignition control module and what type of it is. Usually there is a dwell timing that goes to ICM. Does the pcm supplies voltage or just ground the icm pin, while grounded the coil charges and once the ground is removed the coil fires. I am just speculating. I think this was covered in other threads but can`t find it.

Thanks
Hi,

I will give you all that I have, some hope it will be what you need.

The signal we are speaking about: ignition control is generated by the ESide and connects out through Black or C2 pin 5. The ignition control is both an output and an input (I expect the earlier PCMs are the same). The output is pulled high resistively and an NPN transistor is used bring the signal low. The output is monitored by a mystery chip marked 27474. I think this is a small semi-custom chip like a pal or something. Probably not too much in it.
Your question I think goes to the output type but once dwell comes into it, that is all TPU. Still banging my head on that chip. Some figured out but not all.

Here is the schematic for the bit you are concerned about.

Ignition.jpg

If I didn't answer your question...please ask again

-Tom