Fellow Vetters:

I need a wiring diagram of the wires and their colors that are found inside the pass-through block on the right hand side of the firewall. I can’t figure out why there are 3 pink and white striped wires rather than an even number of two or four. Perhaps two of them are connected and the third is “looped” inside the block and connects to a sensor or device in the engine bay.

Thanks in advance!

SnorT91Man

 

Driver or passenger side?

 

You're on the right track. Do you have the correct FSM for your car? That's a MUST!

Here's a photo of the "loops" in my '84. That's how they connect the engine harness to the chassis harness.

 

I have both the correct FSM and the Sec. 8A Electrical Supplement, but neither shows the wires that are inside the pass-through block on the passenger side of the car. In fact, I can’t find a mention of the block anywhere! I think that some of the wires are looped inside the pass-through block, and therefore, don’t go completely through it or connect to anything in the IP.

SnorT91Man

 

What are you attempting to 'diagnose'? The right side 'pass-through' isn't detailed anywhere but it seems to me that you replaced the engine harness with a correct one by 'part #'. Correct? If you don't have a specific system you're attempting to diagnose I don't understand the concern.

If your concern is PNK/WHT I'd think that if you used the FSM and found the details of C237, C238, C239 & C240 you could answer your question. It wouldn't be simple but doable.

Do you have your old harness?

Check the FSM 8A-203-0 for starters! Do they all have wires that go through the 'pass-through'? I've no idea but you've got all the information available to answer the question that you've asked.

 

After striping down that connector in my 94, there were 3 pink wires. One for each bank of injectors, and one for an Ignition Feed".

Best thing to do if you have questions is to sit down at a table with the harness and probe with a volt meter. Some wires do change colors as they pass through connectors.

 

I appreciate your responses, but I don’t think you understand the problem. First off, I’ve studied 8A Supplement so much that I am 100% sure my problem can’t be answered by it. There are several sets of wires that are looped inside the pass-through block; that is, they don’t pass through it at all. It’s like GM put them there as an easy way to relocate them to a different harness. The three wires I accidentally cut when removing the black gummy stuff around the block are all pink with a white stripe. Now I can’t find any source that will indicate if they were looped in some way (that is actually my guess) or spliced different color wires inside the block.

All of this problem is compounded by the fact that none of the pink/white wires shown in the 8A Supplement are fastened to a C237 through C240 connector, which are the only connectors that “feed” the pass-through block (another reason for assuming they’re looped). I know all of this because my curiosity got the best of me, and I totally disassembled the pass-through block and removed *all* the hard-packed weatherproofing inside it in order to trace every wire coming into it from under the IP.

Finally, there is zero electrical service on the car right now, so it’s impossible to troubleshooting with meters and probes.

Thanks again. I hope the situation isa bit clearer now.

SnorT91Man

 

So the NOS harness you bought actually did come complete with the 'pass through' but you decided to attempt a 'SHORT CUT'!

Where's the 'old harness'?

 

There’s no NOS harness at all. It’s the original 29-year old harness that I am rehabbing, and wanted to clean up by removing all the gunky black weatherproofing stuff on the pass-through block. That’s when I accidentally cut the wires I’m concerned about. Seeing as the cuts were so close to the front edge of the block, I couldn’t splice them. Instead, I had to disassemble the block and pull out all the other wires to reach the cut ones (they’re wedged in groups between “fingers” inside the block). And that is how and why I now have this problem!

SnorT91Man

 

You did buy an NOS though - correct?

https://www.corvetteforum.com/forums...g-harness.html

That harness was correct for a '91, M6 w/C68. - the 'pass through' is in your snapshots! Those snapshots don't show any 'obvious PNK/WHT'!!

 

Forget the snapshots. I was confused about what was what back then. Yes, I did buy an NOS M68 engine and headlight harness that mounts to a two-piece connector on the driver’s side of the firewall, but it’s not the one I’m talking about. In fact, it’s not even in the car right now. Rather, the pink with white stripe wires that I cut are in the pass-through block on the passenger’s side. That entire harness is primarily for sensors and actuators in the engine bay, and doesn’t appear to physically interconnect with the NOS harness at any point.

SnorT91Man

 

You don’t need any electrical hookup. You are checking continuity from terminal to terminal.

Everything that passes through that connector can be traced.