90 GMC Jimmy Wiring Harness

[JeffWithers]

I want to replace my wiring harness, and all i can find are 83-87 Kits. Not sure if that will work well enough. FYI, I will not use anything from Painless, and they are a pain in the ass. American Autowire has the 83-87. Anyone had experience with this.

 

[HankScorpio]

The 88-91 are different. Worse than that pretty much every year in that range was different. It's a TBI truck to start. Things like VSS in the speedometer area come to mind. The overlap with the GMT400 trucks made for some weird things. 91 saw the 4L80E but only in a suburban and crew cab. Things like that make it difficult to say if a harness will work or not. You are going to have to get specific with the harness manufacturer.

 

[JeffWithers]

The 88-91 are different. Worse than that pretty much every year in that range was different. It's a TBI truck to start. Things like VSS in the speedometer area come to mind. The overlap with the GMT400 trucks made for some weird things. 91 saw the 4L80E but only in a suburban and crew cab. Things like that make it difficult to say if a harness will work or not. You are going to have to get specific with the harness manufacturer.

Thanks for the info. Now it makes sense why a kit isn’t available. Since I’m running the Holley Sniper system with built in ECM and a Dakota Digital gauge setup, that narrows down some what needs replaced. The existing wiring has been clobbered up with alarm systems, audio, etc it needs to go. I know I can get a vehicle correct headlight @ taillight wiring kit, so that leaves the ignition & other dash wiring. Thanks again

 

[6872xtc]

I left the speedometer wiring in my '90 Jimmy when I pulled the TBI out to go with the Edelbrock Proflo 4. I removed the factory wiring for the TBI and the original ECM from the original harness by careful sorting. So, if you need the original VSS wires for the Dakota Digital, maybe you can sort it out as you remove the rest. I have no idea if it will work with the Dakota speedometer, hopefully you can find that information. I would think that the connections for the instrument cluster could be handled by ordering with the earlier harness specified, not sure.

 

[92yamaha]

Thanks for the info. Now it makes sense why a kit isn’t available. Since I’m running the Holley Sniper system with built in ECM and a Dakota Digital gauge setup, that narrows down some what needs replaced. The existing wiring has been clobbered up with alarm systems, audio, etc it needs to go. I know I can get a vehicle correct headlight @ taillight wiring kit, so that leaves the ignition & other dash wiring. Thanks again

Out of curiosity, what has been your experience with Painless? I just bought the kit for my 84 K5 and am very impressed. It covers every year of squarebody and nearly every option I know (missing my power back window, though). It's well-organized and labeled throughout. Looks easy enough to me; maybe I'm naive.

 

[JeffWithers]

Out of curiosity, what has been your experien with Painless? I just bought the kit for my 84 K5 and am very impressed. It covers every year of squarebody and nearly every option I know (missing my power back window, though). It's well-organized and labeled throughout. Looks easy enough to me; maybe I'm

Out of curiosity, what has been your experience with Painless? I just bought the kit for my 84 K5 and am very impressed. It covers every year of squarebody and nearly every option I know (missing my power back window, though). It's well-organized and labeled throughout. Looks easy enough to me; maybe I'm naive.

My experience has been limited to a 70 muscle car build and required a lot of connector splicing. Talking about wiring with a few high end custom builders in the past, they all said stay away from Painless. Either way Painless like American Autowire don’t go past 87. I guessing it’s to do with the electronics being added. My 90 has an engine compartment ECM and an under dash ECU (above heater box). That complicates things a bit.

 

[JeffWithers]

I finally order the wiring diagram 250 page GM book for the 1990 Blazer/Jimmy, and the control unit that i thought was an ECM mounted to the brake master cylinder is actually the antilock controller. The ECM is mounted under the dash behind glove box & above heater box, and even without the engine functions taken care of by the Holley Sniper ECM i believe it is necessary for other control functions. Time will tell, and probably going to build my own harness.