1991 V3500 tbi wiring harness

[1-ton]

I figured that is what you meant. Last time I looked at pigtails, the pigtail itself was more expensive than the sensor lol. I used to splice and solder/crimp every cut wire I had, or when I needed to add something, now I just crimp a new terminal to the wire and it's done. Really not any better, but when talking multiple wires, unless you cut each one to a different length, you end up with a knot a few inches from the connector.

I'm curious now, this is not how yours is setup? http://www.ebay.com/itm/CHEVY-GMC-C...0-HEAVY-DUTY-ECM-WIRING-PIGTAIL-/390605663310 24 and and 32 pin if my eyes don't deceive me.

I'm not certain they are correct, but the listings here if sorted by series 100 or micropack 100, seem to look like what is shown in the ebay link. Would really need to dig into the drawing to make sure, if you are lucky the PN might be on the connector body itself. http://www.mouser.com/Connectors/Automotive-Connectors/_/N-1ehb5?Keyword=delphi&Ns=Gender%7c1&No=50&FS=True&P=1z0x3me

Yes, that is it in ebay link. I just did the pin count by multplying the column times the row, even though not all pin connectors are being used...only about half of them if you look at the number of wires coming in on the back side of the connector.

The mouser link makes it look like only the two center rows are used, and not the outside rows. This would match the 24-pin you said.

 

[dyeager535]

I wondered if that is what you were counting. Inner rows are all that are used, the outer ones are how you "unlock" the terminals, and on the back side what the terminal locks insert into as well.

Encouraging to see that at least the design is still available widely. IME what I could buy multiple connectors/terminals for (when I make an educated guess as to what I need) for less than what it cost to buy elsewhere.

They didn't make it real easy when they were building all this stuff, many different connectors and terminals, but those look like the same terminal/connector setup as most ECM's that period, the connector body size/key is probably the only difference.

If you depin one I bet they look like these: http://www.ebay.com/itm/TPI-TBI-Cam...ss-Computer-Connector-Terminals-/360468674105

And I think these are them, but you'd need to do further research as always. GM tended to make small changes that make one terminal look similar to another, until it's in your hand: http://www.mouser.com/Search/Refine.aspx?Keyword=12146447 $.114/terminal if you buy 50. Mouser has been really good on shipping prices. You'd also need a crimp tool of some sort, I'm sure I paid ~$12 for this but don't recall from where http://www.ebay.com/itm/Weatherpack...USA-/231519596210?hash=item35e7a4aeb2&vxp=mtr

 

[1-ton]

I wondered if that is what you were counting. Inner rows are all that are used, the outer ones are how you "unlock" the terminals, and on the back side what the terminal locks insert into as well.

Encouraging to see that at least the design is still available widely. IME what I could buy multiple connectors/terminals for (when I make an educated guess as to what I need) for less than what it cost to buy elsewhere.

They didn't make it real easy when they were building all this stuff, many different connectors and terminals, but those look like the same terminal/connector setup as most ECM's that period, the connector body size/key is probably the only difference.

If you depin one I bet they look like these: http://www.ebay.com/itm/TPI-TBI-Cam...ss-Computer-Connector-Terminals-/360468674105

And I think these are them, but you'd need to do further research as always. GM tended to make small changes that make one terminal look similar to another, until it's in your hand: http://www.mouser.com/Search/Refine.aspx?Keyword=12146447 $.114/terminal if you buy 50. Mouser has been really good on shipping prices. You'd also need a crimp tool of some sort, I'm sure I paid ~$12 for this but don't recall from where http://www.ebay.com/itm/Weatherpack...USA-/231519596210?hash=item35e7a4aeb2&vxp=mtr

I was thinking of using my ECM/PCM connector (or connectors/one is trans management and the other is engine management) as a pigtail, and just cut it off a foot or more from the ECM/PCM as I trace and replace the wiring. Doing a complete ECM/PCM pin-to-pig tail replacment would be quite a job.

 

[dyeager535]

De-pinning the connectors can be done with either a paperclip or small flat blade jewelers screwdriver, won't take much time or effort to de-pin.

Apologies for trying to talk you down this path, but I started out soldering and shrink tubing every connection. When I found out how cheap the components were, and started crimping, I realized how much easier it is than the solder/pigtail method. If you have to run new wire anyway, the only steps are de-pin connector, crimp terminal to wire, insert in connector. That vs. cut wire, flux wire ends, install shrink tube, twist wire ends together, solder wire, shrink tube. Plus working the terminals in the connector a bit more, but that's probably a wash. Although I've had a terminal lock fail, which was fun to figure out.

 

[1-ton]

De-pinning the connectors can be done with either a paperclip or small flat blade jewelers screwdriver, won't take much time or effort to de-pin.

Apologies for trying to talk you down this path, but I started out soldering and shrink tubing every connection. When I found out how cheap the components were, and started crimping, I realized how much easier it is than the solder/pigtail method. If you have to run new wire anyway, the only steps are de-pin connector, crimp terminal to wire, insert in connector. That vs. cut wire, flux wire ends, install shrink tube, twist wire ends together, solder wire, shrink tube. Plus working the terminals in the connector a bit more, but that's probably a wash. Although I've had a terminal lock fail, which was fun to figure out.

I understand what you are talking about...pin-to-pin all the way probobly could be much cleaner and esier than a bunch of splice and solder work, but there is no way out of some solder and splicing because there are some rather dubius multiple connection junctions from the factory, wich are spliced and not even soldered, but just crimped, shrinked, and taped. Thanks for the input...I learned a lot from this.

 

[dyeager535]

You are correct, those weird splices GM does are hard to recreate. I always hated going through the wire loom and finding the wire I was tracing running into one of those lol.

You can also buy crimp pieces that would allow you to replicate those junctions, but they probably used something along these lines to make those. http://www.mouser.com/ProductDetail/TE-Connectivity-AMP/62040-1/?qs=sGAEpiMZZMt24PW2WNEtL4hv62Hdfp6R IIRC they aren't just a barrel type terminal, the crimp ends fold back in on themselves. It's kind of cool being able to recreate the fancy crimps GM used.

 

[POORBOYK5]

What about purchasing the Painless harness and adding the Trans leg to it and changing PCM plugs if needed. At least most of the work would be done. Adding the trans leg would be easier than custom making an entire harness. IIRC painless sells most stock GM wire colors in 10ft +/- sections for adding trans stuff.

The painless harness runs the entire length from the ECM connectors to the engine control input connectors. The wire harness Painless sells has connectors for the 700R-trans ECM, which has different connectors than my 4L80E ECM has.

OK, but still modifying just the trans stuff would still take most of the work out of completely building a new harness. 80% would be done. As for the ECM plugs being different, you can de pin the connector body and install the correct one.

 

[mckustomfab]

Not sure if someone else mentioned it and I just missed it, but you do have a PCM, and the connectors are different the the ECM. I just pulled the harness and PCM out of my '91 R3500 with a 4l80e so that i could swap in a 7747 ECM with a NV4500.

I'm not sure of the quality of Painless Harness but i do agree that you could get the TBI harness they sell and sit down with a wiring diagram and re-pin the connectors that go to the PCM. Then you would just need to run new wires from the 4l80e to PCM connector. Also just in case you don't already know, there is a updated internal and external harness for the 4l80e. I have heard of people using the external harness to build stand alone harnesses. The update changes the connector on the trans I think, so you might have to update both the internal and external harnesses.

 

[1-ton]

OK, but still modifying just the trans stuff would still take most of the work out of completely building a new harness. 80% would be done. As for the ECM plugs being different, you can de pin the connector body and install the correct one.

The transmission wiring harness on my truck is very different from the 700R trans wiring harness. Several of my transmission sensors have "paired wiring" running to them for "noise cancelation". The 700R trans has no "paired wiring" at all. The wiring harness that is on the market for TBI is about $425 with shipping. To pay that much money for a harness I can only use about 50% of would be a lot of money waisted.

 

[1-ton]

Also just in case you don't already know, there is a updated internal and external harness for the 4l80e. I have heard of people using the external harness to build stand alone harnesses. The update changes the connector on the trans I think, so you might have to update both the internal and external harnesses.

Yes, I plan to replace the internal harness on my 4L80E trans, which are all the updated versions. The internal harness on my trans is the original one, and it is leaking. I plan on buying an entire kit, which comes with new internal harnes and updated pigtail, shift solonoids (A&B), pressure solonoid, lock up solonoid, and manifold pressure switch.

 

[Stomis]

Maybe I missed it but couldnt you use a gmt400 harness from a 92-95 4l80e truck? Or does painless not even offer that? I mean they made a damn lot of those trucks, that would be really dumb.

Even if the under hood leg was different you they are split in to. And if the fuse bulkhead is different that would be way easier to repin than the ecm.

 

[1-ton]

Maybe I missed it but couldnt you use a gmt400 harness from a 92-95 4l80e truck? Or does painless not even offer that? I mean they made a damn lot of those trucks, that would be really dumb.

Even if the under hood leg was different you they are split in to. And if the fuse bulkhead is different that would be way easier to repin than the ecm.

there are no after-market wiring harnesses for the TBI/4L80E combo. After-market TBI wiring harnesses where mostly made for the Camaro, Firebird, and Trans-AM crowd. Since 1/2-ton trucks use the same drivetrain, they will work for them as well.

 

[Stomis]

there are no after-market wiring harnesses for the TBI/4L80E combo. After-market TBI wiring harnesses where mostly made for the Camaro, Firebird, and Trans-AM crowd. Since 1/2-ton trucks use the same drivetrain, they will work for them as well.

Thats dumb. I would imagine theres quite a lot of 454 TBI/4l80e and 350 TBI 4l80e 2500s and 3500s out there.

 

[Russell]

Maybe I missed it, but why are you wanting to replace all the wiring on the engine? Is there something wrong with what is already in place?

It might be just as easy to just replace one or two bad wire pairs vs the engine engine harness.

 

[1-ton]

Maybe I missed it, but why are you wanting to replace all the wiring on the engine? Is there something wrong with what is already in place?

It might be just as easy to just replace one or two bad wire pairs vs the engine engine harness.

This truck is 25-years old, and has 200,000 + miles on it. When a vehicle gets that old, and with that many miles, you have to go into great in-depth deatail replacing things, in order for it to be reliable.