95 c 1500 ac and cruise signal wires

Great information, what ecm are you using? Williams Performance said it could be done with a newer ecm also but couldn't tell me how to do it. I'll take your info and try to figure it out on mine. They did say I had to tie into the corvette pedal I'm using. Thanks

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Originally Posted by kewljay223

Did a little more searching. I think i can shed some light but a bit confused on how your set up. you say you removed the old ecm. ok thats fine. but what about the DRAC module? did you toss that too?? If so then i see what the dilema is. But if not, then you still should have the wire that goes to the cruise module because im 99% sure the DRAC is what sends that signal, not the ECM. The DRAC sends 2,000 digital pulses per mile to the ECM (Electronic Control Module), 4,000 digital pulses per mile to the cruise control module, and 128,000 digital pulses per mile to the ABS (Anti-Lock Brake) computer. Your only loss from tossing the old ecm is the speedo signal but the new one can do that provided you "T" into the VSS signal for the new pcm (which i did and it works fine).

So to clear up, they way i understand it, make sure you

1)have the twisted yellow/ppl wires from VSS going to both the DRAC and the new pcm.
2)still have signal wire from DRAC to cruise module (should still be hooked up unless you know you cut it)
3)have speedo hooked up to output of new pcm
4)and obviously still have the 3 or 4 wires from control lever/TCC to cruise unit

i assume you both have #3 done already and im betting # 2 and 4 are still connected. im also betting you cut the twisted pair from vss and put them on the new pcm. i think if you just T off the twisted pair back to the cut pair from inside the cab, this will solve your problems. just make sure to twist the two wires your going to add to cancel out any EMF that the vss creates (the reason they are twisted from the factory).


NOW, if you tossed the DRAC also, well then i still think your ok. If i understand what jeeb was saying on how he plans too hook it up (when you say splice, you are talking about "T-ing" into the wire from pcm to speedo right?), that SHOULD work as the pcm sends out a 4k ppm signal from the factory. and as stated, the cruise wants a 4k ppm signal also. BUUUUT, if you change your gears or tires, you will now need to change the tune to compensate and im not sure how that affects the output. Does changing the the tune change the actuall signal higher or lower going to the speedo? or does it modify the input to output ratio within the pcm to still output 4k ppm no matter what? if so great. but if it changes the actual output, seems to me the speedo will be correct but that means you will be sending a higher or lower ppm to the cruise in which case i have no idea how well it will like that.... may or may not be ok...

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Exactly. That is what my plan is. 4K PPM to speedo/cruise (I didn't know whether the cruise needed 4K or not so thanks for confirming!). And 128K PPM to ABS. When you correct for gears and tire diameters, you are essentially telling the ECM how many full cycles of the sine wave from the VSS (the number of trans output shaft rotations) are in a mile. It then uses that data as well as time and calculates speed. So when you correct for gears and tires it corrects the signal to Speedo, Cruise, and ABS. Then there is no need to keep the DRAC (I tossed it when I found I can get the same data from the LS PCM) Thanks for looking into that!!

Ok, after more research I was told my e38 won't control the cruise control because it has to run through the vette BCM. If I had a 411 with seperate TAC module I'd only have to tie in 3 wires. I was told wrong so disregard what I said about the E38 unless someone knows different.

Im using the 03 pcm that came with my motor and DBW. so all i had to do was hook the lever control wires (like 4) to the TAC module and i was done. thats why im not sure why people are so afraid of it. Its so simple. But to each their own. Anyway, glad i could help out. hopefully that works out for you guys. you should update this either way to confirm or deny that it works.

I think most just get overwhelmed with the thought of wiring and never give it a shot. I will definitely update once I get going on my swap again.

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Originally Posted by kewljay223

Im using the 03 pcm that came with my motor and DBW. so all i had to do was hook the lever control wires (like 4) to the TAC module and i was done. thats why im not sure why people are so afraid of it. Its so simple. But to each their own. Anyway, glad i could help out. hopefully that works out for you guys. you should update this either way to confirm or deny that it works.

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DBW for me wasn't intimidating at all considering how simple it is once you put in a little time and look at a couple wiring diagrams. I'm really glad I decided to stick with it instead of abandoning ship for a DBC setup like a lot of guys. People complain about a throttle response issue but for me that would only come into play if I was looking to minus a few tenths off of my ETs at the track and my big 4x4 is obviously not a race truck. If anything, my throttle is almost too responsive, especially considering how much power I have compared to before with the 350. My wife said when she drove it "it feels like it launches every time you leave a stop light and you have to be careful with the gas pedal"LOL. When I go to a different setup with a bunch of go-fast parts like a stroked out 408 with cnc heads and high flow intake (maybe a bottle) then I'll worry about simplifying my throttle situation.