2001 Chevy Tahoe Wiring Harness

[Matthew Jeschke]

My harness is starting to have issues. Evap is doing weird things. Also when I'm tuning data I notice the Wideband won't read same as PCM unless I tie the grounds together. I think it maybe time to get a new engine wiring harness. Anybody know a good deal for decent quality? I see them all over eBay and amazon (FYI ~ I boycotted amazon). Not sure if they are Chinese junk though.

 

[Matthew Jeschke]

Anybody? Know of a quality replacement wiring harness for GMT800 / 2001 Tahoe?

 

[tooleyondeck]

OEM harnesses are hard to find new. There are some used ones floating around ebay and you can check your local junkyard. Another option is a standalone harness like a Painless or PSI:

GEN III LS (24X) DRIVE-BY-CABLE 4L60/80E & 5 PIN MAF STANDALONE HARNESS

APPLICATION: 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 CHEVROLET, GMC, CADILLAC AND HUMMER TRUCK ENGINES (DRIVE BY CABLE ONLY) WITH MULTEC

www.psiconversion.com

 

[strutaeng]

Wrecking yard from a southern state? Just clean it up and install new loom.

 

[Matthew Jeschke]

Yeah I may have to buy a used one and clean it up. My truck has lived it's life in AZ... It has almost 270k miles on it now. I never have completely removed my harness, however, I rewrapped a bunch of it and cleaned it up. All the wire insulators are melted together, and it's really ragged. Some of the connections are starting to fail too. Right now the purge solenoid for the evap has shorted to something else. I've not had time to diagnose it but I suspect it's getting horrible mileage due partly to that. Sometimes I throw O2 heater codes also. I have fiddled with it trying to fix it up a couple times but getting sick of it.

That painless looks like a good route if money was no object. There's tons of new harnesses on eBay but they're all for like Camaro's and Corvettes. Surprised there's none for the trucks.

 

[strutaeng]

Yeah I may have to buy a used one and clean it up. My truck has lived it's life in AZ... It has almost 270k miles on it now. I never have completely removed my harness, however, I rewrapped a bunch of it and cleaned it up. All the wire insulators are melted together, and it's really ragged. Some of the connections are starting to fail too. Right now the purge solenoid for the evap has shorted to something else. I've not had time to diagnose it but I suspect it's getting horrible mileage due partly to that. Sometimes I throw O2 heater codes also. I have fiddled with it trying to fix it up a couple times but getting sick of it.

That painless looks like a good route if money was no object. There's tons of new harnesses on eBay but they're all for like Camaro's and Corvettes. Surprised there's none for the trucks.

Understand. Most (if not all) of the connectors can be bought and replaced.

I made this post a few months ago: https://www.tahoeyukonforum.com/thr...-engine-transmission-wiring-harnesses.143808/

I've since removed the engine for a rebuild. I replaced the coolant temperature sender pigtail because the little tab had broken on mine. I'm at 262k on my truck, so similar mileage.

The hardest part of removing the harness is the underneath part, especially feeding the long harness down the transmission through the bellhousing. I did by myself, but a buddy helping will make it a lot easier. 4x4 would also complicate things, I think.

 

[Matthew Jeschke]

@strutaeng thanks for the tips! I think a few signals go into the cab for the instrument cluster. Was that a PITA to get those fished out? How did you do those? I'm wondering if a person could just install a connector there to avoid taking the grommet apart.

I called my favorite junkyard. They think they have a harness for me. They're checking... I think I'll swap the new one in and use my old one as a template to possibly build my own harness if I ever find the time. Although I've no clue where to buy all the connectors and different color wire without going broke.

 

[strutaeng]

@strutaeng thanks for the tips! I think a few signals go into the cab for the instrument cluster. Was that a PITA to get those fished out? How did you do those? I'm wondering if a person could just install a connector there to avoid taking the grommet apart.

I called my favorite junkyard. They think they have a harness for me. They're checking... I think I'll swap the new one in and use my old one as a template to possibly build my own harness if I ever find the time. Although I've no clue where to buy all the connectors and different color wire without going broke.

Cool. Hopefully you can source a nice clean harness.

The engine/transmission harness actually does not go into the cab or cluster. There's like 3-4 connectors at the fuseblock for the engine/transmission harness (4x4 models have an extra connector the T-case) and the other main connection is at the ECU. On that thread, I believe I posted a photo of the fuseblock after I removed the engine harness.

At the fuseblock, there's other connectors that I believe go to the cab, and maybe the TAC module on models that have that.

Does your truck have EGR? If so, make sure the donor harness has that. I think somewhere in 01-02 EGR was phased out?