Any idea on this under dash plugs use? 93 c1500

[registered-bum]

I've seen that ... connects to the unobtainium thing.

You must be registered for see images attach

 

[A97obs]

I've seen that ... connects to the unobtainium thing.

You must be registered for see images attach

Forgot to laugh

 

[Road Trip]

The wires are pink/ black stripe and brown , pretty sure it’s just provisional within the harness but not needed .. correct me if I’m wrong

This connector was more of a challenge. I first scoured the '93 Electrical Wiring FSM, and couldn't find what I was looking for.

On a hunch, I switched over to the '94 Electrical Wiring FSM, and discovered the following. The connector *is*
emissions related, but nothing having to do with the fuel vapor canister:

You must be registered for see images attach

So this makes sense. With Federal emissions this connector would remain unused, but if this
vehicle was built with CA emissions this would have been connected to the AIR pump bypass
valve.

Since this diagram tells me that the brown wire is circuit #436, I decided to go back to the '93
FSM and use this unique number to see if I somehow missed this in my first attempt. Circuit
436 didn't get me to the exact spot in the diagrams, but in a table it did associate this number
with the Secondary AIR Injection Solenoid Valve. Searching with part of that phrase did the trick:

You must be registered for see images attach

Note the differences in the way the '93 & '94 wiring diagrams are drawn. For me, the newer style is much
more intuitive than the older style. And again, once I locate a unique circuit #, or connector number, (C118)
or even a less unique hint like the pnk/blk and brn color codes, I can find obscure details like this in a
minute or two on the laptop, instead of an hour or two manually paging through the printed books.

No doubt that the OCR program used to scan in the '94 FSM was configured a little differently than when
the '93 FSM was scanned. I have found that different year .pdf files vary in how well they can be
searched, so sometimes picking a slightly different year FSM to research your GMT400 may improve
your results as long as you stay in your general design era. (TBI '88-'94, {'95 unique}, Vortec '96+)

Don't get me wrong, the paper books are superior if I'm trying to do big picture project research, so
each tool has their place. (Insert a tip of the hat here to the forum members who set us up for success
with the FSM cache.)

Another wiring harness mystery solved. More good practice in the diagrams. Life is muy bueno. :0)

 

[GoToGuy]

Your looking at an online resource. Your first image is out of book two, CK-2 the Emissions and driveability, as noted by the chapter 3A and page 86. The second image is from the large format spiral bound " Electrical Diagnosis and Diagram manual" . As seen by the page number and large wide format. 11 x 16. These are not new. With introduction of the GMT400 the layout was changed for easier use. Some the early PDF are scanned 90 ° rotate to fit the page. It's not the service changed the diagrams. The diagrams in the Emissions manuals are only that specific item circuit. Whereas the Electric diagnostics manuals are the whole circuits and other circuits within a group or sectional area. The computer reference manuals are nice , but is sure is great to have the whole large layout of circuit , wire size, id colors, locations, even the connectors have the part numbers, GM, or Delphi Packard. A ton of great info, easy to use.

You must be registered for see images attach

You must be registered for see images attach

 

[A97obs]

This connector was more of a challenge. I first scoured the '93 Electrical Wiring FSM, and couldn't find what I was looking for.

On a hunch, I switched over to the '94 Electrical Wiring FSM, and discovered the following. The connector *is*
emissions related, but nothing having to do with the fuel vapor canister:

You must be registered for see images attach

So this makes sense. With Federal emissions this connector would remain unused, but if this
vehicle was built with CA emissions this would have been connected to the AIR pump bypass
valve.

Since this diagram tells me that the brown wire is circuit #436, I decided to go back to the '93
FSM and use this unique number to see if I somehow missed this in my first attempt. Circuit
436 didn't get me to the exact spot in the diagrams, but in a table it did associate this number
with the Secondary AIR Injection Solenoid Valve. Searching with part of that phrase did the trick:

You must be registered for see images attach

Note the differences in the way the '93 & '94 wiring diagrams are drawn. For me, the newer style is much
more intuitive than the older style. And again, once I locate a unique circuit #, or connector number, (C118)
or even a less unique hint like the pnk/blk and brn color codes, I can find obscure details like this in a
minute or two on the laptop, instead of an hour or two manually paging through the printed books.

No doubt that the OCR program used to scan in the '94 FSM was configured a little differently than when
the '93 FSM was scanned. I have found that different year .pdf files vary in how well they can be
searched, so sometimes picking a slightly different year FSM to research your GMT400 may improve
your results as long as you stay in your general design era. (TBI '88-'94, {'95 unique}, Vortec '96+)

Don't get me wrong, the paper books are superior if I'm trying to do project research, so each tool has their
place. (Insert a tip of the hat here to the forum members who set us up for success with the FSM cache.)

Another wiring harness mystery solved. More good practice in the diagrams. Life is muy bueno. :0)

KYour way more

This connector was more of a challenge. I first scoured the '93 Electrical Wiring FSM, and couldn't find what I was looking for.

On a hunch, I switched over to the '94 Electrical Wiring FSM, and discovered the following. The connector *is*
emissions related, but nothing having to do with the fuel vapor canister:

You must be registered for see images attach

So this makes sense. With Federal emissions this connector would remain unused, but if this
vehicle was built with CA emissions this would have been connected to the AIR pump bypass
valve.

Since this diagram tells me that the brown wire is circuit #436, I decided to go back to the '93
FSM and use this unique number to see if I somehow missed this in my first attempt. Circuit
436 didn't get me to the exact spot in the diagrams, but in a table it did associate this number
with the Secondary AIR Injection Solenoid Valve. Searching with part of that phrase did the trick:

You must be registered for see images attach

Note the differences in the way the '93 & '94 wiring diagrams are drawn. For me, the newer style is much
more intuitive than the older style. And again, once I locate a unique circuit #, or connector number, (C118)
or even a less unique hint like the pnk/blk and brn color codes, I can find obscure details like this in a
minute or two on the laptop, instead of an hour or two manually paging through the printed books.

No doubt that the OCR program used to scan in the '94 FSM was configured a little differently than when
the '93 FSM was scanned. I have found that different year .pdf files vary in how well they can be
searched, so sometimes picking a slightly different year FSM to research your GMT400 may improve
your results as long as you stay in your general design era. (TBI '88-'94, {'95 unique}, Vortec '96+)

Don't get me wrong, the paper books are superior if I'm trying to do project research, so each tool has their
place. (Insert a tip of the hat here to the forum members who set us up for success with the FSM cache.)

Another wiring harness mystery solved. More good practice in the diagrams. Life is muy bueno. :0)

kudos to your ability and efforts to be able to navigate and understand systems like these that I can’t even wrap my brain around hardly . I guess some emissions and some electrical I get but mostly that’s where it stops for me .
I know basics I’m more on the mechanical and definitely suspension side of these trucks .
Normally you don’t have to scavenge a wiring issue or dilemma on these older trucks, they are rather plain Jane , but it pays off to know How to read a schematic .

My 99 suburban is CA Emissions and has the electrical sai pump ! Although it’s a vortec and the pump is placed differently along the driver side on fender and looks different than a 88-94 tbi sai pump I assume.

That would have eliminated me from even knowing that plug was routed in place for that particular pump .
At least I was in the general vicinity of knowing it was something provisioned .
Appreciate the help

 

[Road Trip]

KYour way more

kudos to your ability and efforts to be able to navigate and understand systems like these that I can’t even wrap my brain around hardly . I guess some emissions and some electrical I get but mostly that’s where it stops for me .

I was once in your shoes with this stuff. Athough I was a motivated student (ie: if I didn't fix my
car myself I was reduced to walking or bumming rides from friends) ...I would get stuck on electrical stuff.
Fortunately for me there always seemed to be an elder who was willing to answer my questions/mentor me.

At the time I didn't understand why they would take the time & trouble to do this. But ~50 years later I now get it.

They had spent a lifetime accumulating hard-won skills, and they didn't want all this to just disappear into thin air
when it was time to head towards the pearly gates. :0) Instead, they were hoping to pass it on to interested
members of the next generation. For this is the same way that my elders got their start way back when.

Handing down skills like this is a time honored tradition that goes back generations and helped to make
America the place where skilled people make things work. (!)

I know basics I’m more on the mechanical and definitely suspension side of these trucks .
Normally you don’t have to scavenge a wiring issue or dilemma on these older trucks, they are rather plain Jane , but it pays off to know How to read a schematic .

My 99 suburban is CA Emissions and has the electrical sai pump ! Although it’s a vortec and the pump is placed differently along the driver side on fender and looks different than a 88-94 tbi sai pump I assume.

That would have eliminated me from even knowing that plug was routed in place for that particular pump .
At least I was in the general vicinity of knowing it was something provisioned .
Appreciate the help

My pleasure. Wiring diagrams can be frustratingly inscrutable when you first try to use them.
But with practice over time they can tell you so much more than you would think at first glance.
And instead of people giving up on a long time family (GMT400) member, if I can show them that
electrical gremlins are not to be feared, but systematically tracked down and eliminated, then this
simply feels like a good use of my time. And it's fun when someone reports that they fixed an
issue that had been been resisting repair & others had given up on.

By the way, most of us are concrete learners. Working on mechanical stuff is intuitive & makes sense.
On the other hand, reasoning through invisible waves of electrical power favors abstract learners. But
if a really concrete learner like myself can add electrical circuits to my mechanical comfort zone than
*anyone* can. It takes time. (And for me the water analogy was a big help when it came to current flow
and other tough spots.)

Thanks for your feedback. It's appreciated.