DIS question..

[RoboGeek]

does the PCM or the ICM decode the crank trigger signal for coil pack firing? I have found both theories and I aint sure which is correct. My wiring diagrams show the crank trigger running to the PCM on one page and on the next the crank trigger runs directly to the ICM with just a ign. control out and ign. module bypass on the PCM connecting them.
So they are contradicting themselves.
I'm trying to figure how the crank trigger is decoded for #1 cyl so I can figure out a winter test bench setup..

[32v_dohc]

For the early stuff like my northstar, the ICM decodes the signal and the pcm recieves a signal similiar to what the ICM of a distributor would put out. For the northstar specifically the engine has two crank sesnors that read the teeth on the crank and create a unique pattern. The ICM decodes this pattern to find position and establish the first cylinder. The ICM also generates a 4X and a 32X signal for the PCM. As an aside the ICM also reads the camshaft sensor and sends a high or low signal to the PCM that lasts 1 rev then changes and lasts 1 rev.

HTH

John

[RoboGeek]

thats what I'm hoping mine does too.. I have no cam trigger just crank trigger.