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'72 K5 - BYT - 1 ton swap

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wiring harness work has started!
I made a table up out of a 4x8 sheet and laid it out as best I could. Here is the unmodified harness I started with:
Harness1.jpg


Thanks to Bigblock72 for printing me off the 15 pages :eek1: of wiring schematics to go with it.

Here is the harness stripped of all the loom and tape:
Harness2.jpg


As per another suggestion by Bigblock72, I used zip ties to keep the wiring together while still having all of the loom and tape off so I can work with it.

So far so good. I labeled as many connectors as I could with white electrical tape and now that I can see everything I'll get the rest labeled up by tracing the wires back to the computer. Then it will be time to start stripping out anything I don't need anymore. :woot:

One quick question... what the hell is this thing?
Part1.jpg
 
That is the neutral safety switch off of the side of a 4l60e. You won't need it or the round gray connector (top left in your picture) for your installation.
 
I just did this a couple months ago myself. Its really not too bad doing it one step at a time. Best thing was following the instructions on lt1swap.com.
 
bigblock72 said:
That is the neutral safety switch off of the side of a 4l60e. You won't need it or the round gray connector (top left in your picture) for your installation.
Click to expand...
cool, thanks! I'm probably going to leave the connector in the harness though. I may change my mind at some point and put in an auto tranny.
 
ashman said:
cool, thanks! I'm probably going to leave the connector in the harness though. I may change my mind at some point and put in an auto tranny.
Click to expand...

Even if you put in an auto tranny you won't need that, it's just a gear sensor and safety switch/reverse light switch, which are already built into the steering column of our old rigs. The large round connector on the back of the tranny near the pan is what actually controls the transmission, don't cut that one off the harness. :waytogo:
 
ashman said:
wiring harness work has started!
I made a table up out of a 4x8 sheet and laid it out as best I could. Here is the unmodified harness I started with:
Harness1.jpg


Thanks to Bigblock72 for printing me off the 15 pages :eek1: of wiring schematics to go with it.

Here is the harness stripped of all the loom and tape:
Harness2.jpg


As per another suggestion by Bigblock72, I used zip ties to keep the wiring together while still having all of the loom and tape off so I can work with it.

So far so good. I labeled as many connectors as I could with white electrical tape and now that I can see everything I'll get the rest labeled up by tracing the wires back to the computer. Then it will be time to start stripping out anything I don't need anymore. :woot:

One quick question... what the hell is this thing?
Part1.jpg
Click to expand...


Put some wood screws with heat shrink over them into the osb to help keep connectors in place while stripping and cutting. I know it doesn't sound like it helps but it helps a lot keeping the harness from not falling on the floor. I usually put two side by side on an angle to make a notch ( /\ ) then you can slide new wires in and take wires out.
 
y5mgisi said:
I just did this a couple months ago myself. Its really not too bad doing it one step at a time. Best thing was following the instructions on lt1swap.com.
Click to expand...
Yeah, I have your thread bookmarked along with a few others. :D

I would love to do an LS swap. But that is the biggest reason that keeps me away. All those wires.
Click to expand...
So far the wiring harness has been a lot less complicated than expected. You're more than welcome to come take a look anytime. If things go well, maybe we're doing a swap in your truck next. :pimp:

Even if you put in an auto tranny you won't need that, it's just a gear sensor and safety switch/reverse light switch, which are already built into the steering column of our old rigs. The large round connector on the back of the tranny near the pan is what actually controls the transmission, don't cut that one off the harness.
Click to expand...
hmmm, I'm pretty sure my reverse light switch was a plug in the top of my tranny... I don't have an auto now so I don't think my column has any of that stuff.

Put some wood screws with heat shrink over them into the osb to help keep connectors in place while stripping and cutting.
Click to expand...
Good call, I'll be doing that.
 
passed another wiring milestone today. I went through every pin on the PCM and labeled every wire/connector. Now that that is done, it's time to start marking out what I plan on removing. I'll be posting a list here for input for sure!

Also, got a little something in the mail:
Oil_port_adapter.jpg


Oil cooler lines deleted. :thumb:
 
NorCal69 said:
Where does that new part go on a BB? :tongue1:
Click to expand...
lol, you know it honestly came down to what I could get a good deal on between going 6.0 and 8.1. There are pluses and minuses to both but joining the BB club would have been fun. :D
 
Ok, I think I have the first pass at a remove list done. Any advice is certainly welcome!

C1:

pin 13: requested torque signal (traction control?)
pin 23: low reference for fuel tank pressure
pin 25: HO2S bank 2 sensor 2
pin 28: HO2S bank 1 sensor 2
pin 30: coolant level
pin 38: damping lift/dive signal (dunno?)
pin 45: 5-volt reference for A/C
pin 46: fuel tank pressure
pin 65: HO2S bank 2 sensor 2
pin 68: HO2S bank1 sensor 2

C2:

pin 3: dual tank fuel pump relay
pin 5: delivered torque signal (?)
pin 14: A/C refrigerant pressure sensor
pin 43: A/C compressor clutch
pin 52: HO2S bank 1 sensor 2
pin 53: HO2S bank 2 sensor 2
pin 64: fuel tank pressure
pin 73: fuel level -secondary
pin 80: low ref A/C

I decided to go ahead and remove the A/C stuff. I'll keep the wires and compressor around just in case, but the chances of my ever installing A/C on this truck are pretty slim.

I did have a couple of questions on a few pins though.
C1 pins 58,59 class 2 serial data. what are these pins used for?

C2 pins 34, 45 EVAP canister. what are these pins for?

If this list is good to go, I'll remove these wires, the connectors they go to and the various other wires associated with them and be about ready to fit whats left to the truck. :thumb:

*edit*
Just looked over the list at lt1swap.com and it looks like I can remove a few more wires.

C1:
pin 7: 5-volt reference for oil pressure sensor (don't I want that??)
pin 39: starter enable relay (am I just bypassing that?)
pin 56: for flex-fuel. (already not in this harness)
pin 59: class 2 serial data (I guess I need pin 58, but not this one?)
pin 63: low reference for oil pressure (don't I want that?)
pin 70: oil level switch

C2:
pin 34: EVAP purge (guess I don't need this after all)
pin 45: EVAP vent
pin 49: vehicle speed (looks like I only need pin50 for my speedo)
pin 54: fuel level sensor (oh yeah, wiring directly to my gauge)
pin 58: oil pressure sensor (again, don't I want that?)
pin 59: crank voltage (?)

Anybody have any insight into the oil level and oil pressure pins?
 
Last edited:
Class 2 serial data could be obdII port? And evap is emissions stuff. Did you look over the list at lt1swap.com?
 
On the oil pressure stuff, I do believe that is just info collected by the computer and sent out to the gauges/body control module. So no, you don't need that stuff. Also, starter relay isn't needed. Originally the computer controlled the starter relay. For our trucks, we wire them up like the original truck with the wire going straight from the ignition switch to the starter.
 
ashman said:
Ok, I think I have the first pass at a remove list done. Any advice is certainly welcome!

C1:

pin 13: requested torque signal (traction control?) It is for ABS and traction control
pin 23: low reference for fuel tank pressure
pin 25: HO2S bank 2 sensor 2
pin 28: HO2S bank 1 sensor 2
pin 30: coolant level
pin 38: damping lift/dive signal (dunno?)
Pin 39: Starter relay
pin 45: 5-volt reference for A/C
pin 46: fuel tank pressure
pin 65: HO2S bank 2 sensor 2
pin 68: HO2S bank1 sensor 2

C2:

pin 3: dual tank fuel pump relay
pin 5: delivered torque signal for ABS
pin 14: A/C refrigerant pressure sensor
pin16: 4wd low signal from transfer case
pin 43: A/C compressor clutch
pin 49: VSS signal to ABS
pin 52: HO2S bank 1 sensor 2
pin 53: HO2S bank 2 sensor 2
pin 64: fuel tank pressure
pin 73: fuel level -secondary
pin 80: low ref A/C

I decided to go ahead and remove the A/C stuff. I'll keep the wires and compressor around just in case, but the chances of my ever installing A/C on this truck are pretty slim.

I did have a couple of questions on a few pins though.
C1 pins 58,59 class 2 serial data. what are these pins used for?

C1 58 goes to DLC pin 2, I don't know what C1 59 is used for

C2 pins 34, 45 EVAP canister. what are these pins for?

C2 34 is for evap purge solenoid that is mounted in the intake manifold and is not needed. C2 45 is for the evap vent solenoid and also isn't needed.

If this list is good to go, I'll remove these wires, the connectors they go to and the various other wires associated with them and be about ready to fit whats left to the truck. :thumb:

*edit*
Just looked over the list at lt1swap.com and it looks like I can remove a few more wires.

C1:
pin 7: 5-volt reference for oil pressure sensor (don't I want that??)
pin 39: starter enable relay (am I just bypassing that?)
pin 56: for flex-fuel. (already not in this harness)
pin 59: class 2 serial data (I guess I need pin 58, but not this one?)
pin 63: low reference for oil pressure (don't I want that?)
pin 70: oil level switch

C2:
pin 34: EVAP purge (guess I don't need this after all)
pin 45: EVAP vent
pin 49: vehicle speed (looks like I only need pin50 for my speedo) Pin 50 is an output that you could connect to an electronic speedo, I don't know what the pulse rate is though.
pin 54: fuel level sensor (oh yeah, wiring directly to my gauge)
pin 58: oil pressure sensor (again, don't I want that?)
pin 59: crank voltage (?)tells computer when engine is cranking and can help engine start easier, though is not mandatory

Anybody have any insight into the oil level and oil pressure pins?
Click to expand...
The oil level sensor is to light a low oil warning on the dash. The oil pressure sensor is only for instrument cluster and has no effect on anything else.
 
thanks BB72. I've been on vacation but it's time to get this wiring harness finished up so that I can get on to the rest of the swap.
 
I've about got my wiring harness all finished but I have a couple of questions left.

I have a wire coming from the alternator that went to the C100 connector that connects to the interior of the truck.

ScreenShot2013-12-14at10337PM_zpsd2a163b2.png

It connects to pin J in the above image. What is this wire for? Is it for a voltmeter or ammeter?

Also, I added pins for controlling my electric fans to the PCM connectors. C1-42 and C2-33. How are these wires supposed to be connected? I think I heard that they will provide ground to the fan relays to turn on the fans. Is that correct?

And one last question. I have a lt Blu wire coming from the throttle position controller that goes to the old fuse block. I can't seem to find what I'm supposed to do with that one either. :dunno:
 
The dark blue wire coming out of pin a of the alternator goes to c100 pin j and is used for the vacuum pump on the brake booster on '03 and older applications ('04-05s had hydro-boost)and is not needed.

The PCM runs the ground side of the relay.

The lt blue wire at c1-6 from the TAC module is a brake light input to disable cruise control.
 
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