3500hd wiring harness

[chevyCowboy]

I recently purchased a 98 3500 HD and the wiring harness is a mess


I pulled it put out and have another one out of a 00 3500 that I was going to swap it out with.

the one I was going to use as a replacement is from an automatic transmission truck and the 3500 HD is a manual transmission.

I was comparing the pins on the c100 connector which goes to the firewall on the driver side and the automatic transmission harness has a few extra pins that the manual transmission one does not. I'm guessing this will not be a problem. the only pin that I have found that is missing from the automatic transmission harness that was in the manual transmission harness is something to do with diagnostic signal ABS diesel.

I found that because I have a set of factory manuals and was comparing the pin outs.

also on the harness where it plugs into the ECM I noticed that there are more pins on the automatic transmission harness then the manual one.

from what I can tell, there are all the same pins that are in the manual. transmission harness are in the automatic transmission harness. there are just extra ones in the automatic transmission harness.

I am thinking that that will not be a problem because obviously there's no female side of the pins on the other connectors.

has anybody messed with this before? can anybody shed any light?



automatic left manual right

 

[dbrannon79]

If your just using the under hood harness, you should be fine. I would de-pin the one for the ABS and put that one into the one your using so just in case you ever want the ABS to function. also without it, the light will be on in the dash too. on the 2000 one, some of the connectors that go to things like the ABS and other sensors might be different configurations. be sure to verify this.

other than this, with the harness out of the engine compartment, you can check and do any repairs on you old one plus loom it up how you like cleaning it up so it looks pretty! there are things under the hood that you might want to relocate like say the PMD. you can pull the wires from it out from going to the intake, reroute them down the drivers fender to meet the extension to get to the front bumper. relocate the FFM to the fender too if you would like it out of the way and easy to get to. I have mine sitting next to the master cylinder. wire in the relay mod for the OPS keeping it all in the loom integrating an override switch for priming and testing placing it next to the FFM on the fender too.

There are two 10mm studs on the under hood fuse block which you can feed power to things like relays. heck even doing the quad headlight mod too so that both high and lo are on with the high beams, all that requires is adding a relay and a small amount of wiring to the headlight harness on the drivers side for that.

wire in an override push button to the GP controller, just tap into the yellow wire to the controller and feed it switched 12+ from a push button gets you a manual GP operation without doing anything to the PCM timing them on the first start.

Lots of optimizations you can do some of which GM should have done from the get-go!

 

[chevyCowboy]

If your just using the under hood harness, you should be fine. I would de-pin the one for the ABS and put that one into the one your using so just in case you ever want the ABS to function. also without it, the light will be on in the dash too. on the 2000 one, some of the connectors that go to things like the ABS and other sensors might be different configurations. be sure to verify this.

other than this, with the harness out of the engine compartment, you can check and do any repairs on you old one plus loom it up how you like cleaning it up so it looks pretty! there are things under the hood that you might want to relocate like say the PMD. you can pull the wires from it out from going to the intake, reroute them down the drivers fender to meet the extension to get to the front bumper. relocate the FFM to the fender too if you would like it out of the way and easy to get to. I have mine sitting next to the master cylinder. wire in the relay mod for the OPS keeping it all in the loom integrating an override switch for priming and testing placing it next to the FFM on the fender too.

There are two 10mm studs on the under hood fuse block which you can feed power to things like relays. heck even doing the quad headlight mod too so that both high and lo are on with the high beams, all that requires is adding a relay and a small amount of wiring to the headlight harness on the drivers side for that.

wire in an override push button to the GP controller, just tap into the yellow wire to the controller and feed it switched 12+ from a push button gets you a manual GP operation without doing anything to the PCM timing them on the first start.

Lots of optimizations you can do some of which GM should have done from the get-go!

Thanks.

I checked and all of the connectors seem to be the same other than the one from the automatic transmission obviously has a whole bunch of plugs for that.

 

[Glagulator]

A2 - AUTO TRANS 12V. IGN - NOT NEEDED
B2 & B3 - NOT USED 3500HD
C2 - PARK/NEUTRAL SAFETY SWITCH - NOT NEEDED
D1 - ABS DIAGS GOES TO DLC - 3500HD ONLY

Are there terms on the firewall conn. for any of the above terms?

 

[chevyCowboy]

A2 - AUTO TRANS 12V. IGN - NOT NEEDED
B2 & B3 - NOT USED 3500HD
C2 - PARK/NEUTRAL SAFETY SWITCH - NOT NEEDED
D1 - ABS DIAGS GOES TO DLC - 3500HD ONLY

Are there terms on the firewall conn. for any of the above terms?
View attachment 95485

so I should probably try and figure out the abs diag one

 

[chevyCowboy]

A2 - AUTO TRANS 12V. IGN - NOT NEEDED
B2 & B3 - NOT USED 3500HD
C2 - PARK/NEUTRAL SAFETY SWITCH - NOT NEEDED
D1 - ABS DIAGS GOES TO DLC - 3500HD ONLY

Are there terms on the firewall conn. for any of the above terms?
View attachment 95485

also just curious how did you find these It took me forever to find the right page in the manuals I have to figure out what goes to what

 

[Glagulator]

I build the harnesses for these diesels.
Did you see my question about existing terms?
FYI the FSM's are full of errors.

 

[chevyCowboy]

I build the harnesses for these diesels.
Did you see my question about existing terms?
FYI the FSM's are full of errors.

so the other side of the plug? I didn't look but I can when I get back home. what would I need to do get the abs diags to work

also where do you build harnesses at. I looked all over trying to find a place to buy a harness

 

[chevyCowboy]

I build the harnesses for these diesels.
Did you see my question about existing terms?
FYI the FSM's are full of errors.

best I can get but looks to me like the same ones are not there on both sides