For background info on my swap visit

https://www.thirdgen.org/forums/ltx-...zz-95-lt1.html.

Basics are that I am swapping 95 LT1/T56 into my 87 L98/T5 (converted trans few years back). I am rather pleased with my harness progress, it all makes sense and checks out correct...let's hope it works though! I have 2 questions and I think I can finish it up.

1) on LT1 clear harness C14 Brake Switch Signal Lt BLU/BLK my harness does not have this wire. Is that because it's a manual trans and therefore it is not needed? In which case I can ignore this wire for my swap?

2) where is the most logical location to get + 12V during cranking?

 

don't know about 1, but i'd think that the ignition switch would be the answer to #2.

 

I figure that I want an ignition wire but where to pull it from? The purple wire on the 3rd gen c100 which goes to the starter, was my guess or should I go right to the steering column and try to find it near the ignition?

 

For #1, I can't say I know specifically, but that's a pretty good guess. Did the donor car have cruise control?

For #2, yes, you can tap the purple start wire for a 12v start signal to the PCM.

 

1) Correct. For autos it is used for TCC, for manuals, only cruise. No cruise, no need

2) C100 B4 PPL for 12v only while cranking. If you want IGN for say the coil, use C100 F4 PNK. Other IGN points will all be at the C207/C221 for 87

 

Thanks for the response guys. Also thanks pocket for the 3rd gen harness write, you pics made it intimidating at first but once you get into its, rather straight forward and often common sense. Just to discuss further for my understand, because I like to understand why not just how. I am perplexed with this C14 now. There is no wire but the car does have cruise, the switch is there the module and cable are there but the wire isnt. That would explain why the cruise wasn't working in the 95. Perhaps the ECM in the 95 is not original, even though everything else followed exactly all the pinouts. Makes me wonder if I will be able to make cruise work in my 87 after the swap.

Secondly pocket I didn't fully understand your explanation of the cranking 12v. So if I use the C100 B4 that's fine? However if I need another source down the road, I should use c100 F4? The wire I am looking for 12v cranking is the black connector 30 (PCM ignition positive voltage).

 

Whats the C14?

Cruise is its own mini harness under the steering column for 3rd gens and build into the engine bay/lights harness for 4th gens. I wrote a thread on adapting digital cruise boxes to LT1/LSx conversions a few years ago

You asked about cranking 12v, so thats 12v only when the engine is cranking and the only circuit in the whole car that meets that is the starter circuit. I cant imagine why youd need to tap into that for anything other than a car alarm. Thats the C100 B4 ppl

F4 is unfused 12v IGN strait from the IGN switch on the column. It originally fed the IGN coil. I dont use it at all for LSx, but LT1s still use it to feed the coil. 12v IGN is commonly referred to as 12v switched or simply IGN. That means its live for all key positions except off and accy. 12v cranking means its live only when the key is at the start position. 12v constant or batter 12v means hot at all times regardless of key position. 3rd gen key positions are ACCY, OFF, RUN and START

PCM IGN B30 and D3 both need to come off the ECM fuse, C207 pin F (all years)
PCM batt B15 and B31 need to tie into the fused FP relay hotside. There is an external connector near the battery with a 20A fuse and cap for this

 

[QUOTE=Pocket;5927888]Whats the C14?


OK I think I am getting there. Sorry C14 is that 14 pin on the clear connector, for the brake switch. For now I am going to do nothing with it, since my 95 ran fine without it (except the cruise didn't work, not sure if that the reason). As for the cranking volts it wasn't making sense to me to require 12V during cranking but based on a post I was following that's what I assumed it meant (perhaps I misunderstood the terminology). Here is a copy of the page I have been working off of.....


C230 Blue 10 pin connector
------
[K] [J] [H] [G] [F]
[A] [B] [C] [D] [E]
G Pink Needs to receive Cranking 12 volts



.....so I should take this G Pink wire and connect it to F4 to feed the coil not a cranking 12V. Thanks for help it is greatly appreciated. I am new to all this and really enjoying so far, thanks to people like you who have taken time to do write ups to help others. I am trying to do that with my swap thread to add to the info out there.

 

For 95 C230 pin G is PCM 12v IGN fuse

http://shbox.com/1/harness_connector_faces.htm