I am in the middle to end of putting a sbc 400 in my 72 Blazer. I have just about everything worked out and working, except I can not get a seep signal to the computer. I am useing a 4 ppr vss into a drac into the computer. I can't seem to find the info on how to diagnose the components,mainly the drac output signals.

 

What computer are you using?
The VSS wiring to computer varies by ECM type

 

Its an ebl flash, 747 computer. I am mostly looking for what voltage I should see out of the drac. I did some more testing and I think I have two bad dracs. I get a poor square wave out of them, but when I tap them the signal changes.

 

I thought the drac uses 20ppm input? can you change it from your 4k to a 2k and uses a vss buffer to get the optical 2k to the ecm? if not looks like dakota digital sgi-5 would be the answer.

 

I made a mistake, its the output that I was looking for. With a little more digging and googling the question diferently I think I found the answere that makes the most sense. The drac output is a 5 volt dc square wave. If this is true I can now dig thruogh more junk and find one that works.