1998 454 in 1996 C1500 with 0411 PCM. No fire

[bluex]

-There's a difference in the (primary) firewall plug wiring layout for the '96 and '98, causing interior power issues

I'll take this category for $1000 Alex.

Pretty sure that's where your issue is...

 

[VorTecxas]

I'll take this category for $1000 Alex.

Pretty sure that's where your issue is...

But what would it be? What would they change? I've looked around and every diagram I find says its the same for '96-'00. I guess I'm on the hunt for a '96 harness...

 

[bluex]

But what would it be? What would they change? I've looked around and every diagram I find says its the same for '96-'00. I guess I'm on the hunt for a '96 harness...

I think your best bet would be to check some GM manuals for each year an see if anything is different. It could be a difference between the heavier duty trucks an the lighter ones?

 

[454ss]

bingo! half ton to hd25 or 3500

 

[VorTecxas]

I'll go to GMC and see what they have on Monday, but others have done this swap before and I can't find anything on them having these issues. Thanks for ya'lls input, if anyone has anything else to add I'm all ears.

Do ya'll think it would be simpler for me to get a body side harness from a '98-'99 2500 or 3500 and use it? I have to change out my dash anyways, its cracked to hell

 

[VorTecxas]

After some research and talking to Jeff (Lextech, thanks for all of your help, by the way), I have narrowed it down that the most probable cause is that the '96 under dash harness is more than likely not compatible with the '98 engine harness. Looks like I'm doing my dash sooner than planned.

I'm not 100% that it will work, but since I have to anyways, might as well. Prayin to the truck gods to smile on me.

 

[Vortec Lover]

Good luck man... how long has the truck been out of comission now?

 

[VorTecxas]

Good luck man... how long has the truck been out of comission now?

5 weeks, 1 day, 6 hours

 

[VorTecxas]

2 of those weeks due to this, 1 week spent waiting on the PCM. I had it done in 2

 

[great white]

After some research and talking to Jeff (Lextech, thanks for all of your help, by the way), I have narrowed it down that the most probable cause is that the '96 under dash harness is more than likely not compatible with the '98 engine harness. Looks like I'm doing my dash sooner than planned.

I'm not 100% that it will work, but since I have to anyways, might as well. Prayin to the truck gods to smile on me.

Sounds entirely likely. The OBDII trucks are significantly different in wiring aspects.

Since you've got issues with both chassis and engine systems, it's something that's common to both.

That would be the wiring harness.....