05 OEM E-Fan harness in 03 Yukon questions

[Dan Acosta]

I know this has been discussed quite a bit. I have read a lot of posts and pages, which is why I am here. I think the info has gotten a bit confusing to me.

I have an 03 Yukon. I want to wire the OEM harness like the factory did in 05 (I think).

Can someone simply tell me how to wire the harness for an 03 and also let me know where/ how the relay panel is mounted?

 

[Dan Acosta]

OK, Figured out where the relay panel gets mounted. I didnt realize I had to remove the fender brace & cover panel (not lid). Now, I just want to confirm the wiring pin location for the 03 and up models. Thanks

 

[ScottyBoy]

The relay block sits right alongside the underhood fuse box, but UNDER the cover/shroud. To remove the fuse box shroud, you will have to unbolt that curved corner brace that bolts to the fender and wiper cowl. Once you take those four 13mm bolts out, that brace will come right out then you can lift the fuse box shroud straight up once you release the tabs that hold it clipped on. You may have a wiring harness or two clipped on to the front if the fuse box shroud that you have to remove as well. Once you get the shroud off, then pay attention to the actual fuse block. One corner is the main feed and this wire feeds directly to the battery. This is where your power supply for the fan relay block will connect to. You need a 7mm socket to take that loose. I suggest removing the negative battery cable first. Also pay attention to how the fuse box is clipped in place. If you unclip the side towards the driver's side fender, you can flip it up, side the other side is basically hinged on two pins. Release those clips and flip it up because you will want to run the fan harness UNDER the fuse block and clip the fan relay block just to the right side of the fuse box(if viewing from the driver's side of the truck). You should clearly see where the relay block fits into, it looks like it was made to fit there. Once you get that clipped in, the harness ran under the fuse box, then clip the fuse box back down, connect your power supply I previously mentioned. Then the part of the fan harness with the two ECM trigger pins will need to be routed to the PCM, and plugged in to the PCM. To to that, you will have to unclip the tabs holding the PCM in place, then undo the two 7mm bolts that hold the harness to the PCM. route your two fan pins in, and you will want to plug the green trigger wire into the BLUE plug pin #42. The blue trigger wire goes to pin #33 in the GREEN plug. A little silicone grease helps a lot when sliding those pins in place. Be very careful removing the PCM harness caps/covers so you don't break them, use a small screwdriver or a pick tool. Now once you get the PCM part out of the way, start running the rest of the fan harness alongside the wire loom that runs from the fuse box down towards the radiator core support. Use some zip ties to secure your fan harness in place to that existing harness. When you get to the bottom of the core support, go towards the passenger side and keep securing the harness alongside the existing factory harness along the bottom of the radiator support. Your fan plugs should line right up in the middle of the radiator if you did everything properly so far. Now take the rest of the harness and keep running it towards the passenger side, and find a good place to ground it on the passenger side frame rail. On the 05-06's, there is a bolt where the harness grounds to the frame just below the frame horn, behind the bumper. On my 2001, my horn is in that area, so I grounded mine using the bolt that holds the horn in place to the frame rail. So now once you get all that done and secured, just plug your fans in (assuming you already mounted your electric fans) and then you are done.

For a little more info and a few pictures, go look at the thread I made when I installed my electric fans. https://www.tahoeyukonforum.com/threads/i-installed-e-fans-on-my-2001.28336/

 

[Tonyrodz]

OK, Figured out where the relay panel gets mounted. I didnt realize I had to remove the fender brace & cover panel (not lid). Now, I just want to confirm the wiring pin location for the 03 and up models. Thanks

Got a pic of how you have yours? Did you have the fans turned on(flashed) through the pcm already?

The relay block sits right alongside the underhood fuse box, but UNDER the cover/shroud. To remove the fuse box shroud, you will have to unbolt that curved corner brace that bolts to the fender and wiper cowl. Once you take those four 13mm bolts out, that brace will come right out then you can lift the fuse box shroud straight up once you release the tabs that hold it clipped on. You may have a wiring harness or two clipped on to the front if the fuse box shroud that you have to remove as well. Once you get the shroud off, then pay attention to the actual fuse block. One corner is the main feed and this wire feeds directly to the battery. This is where your power supply for the fan relay block will connect to. You need a 7mm socket to take that loose. I suggest removing the negative battery cable first. Also pay attention to how the fuse box is clipped in place. If you unclip the side towards the driver's side fender, you can flip it up, side the other side is basically hinged on two pins. Release those clips and flip it up because you will want to run the fan harness UNDER the fuse block and clip the fan relay block just to the right side of the fuse box(if viewing from the driver's side of the truck). You should clearly see where the relay block fits into, it looks like it was made to fit there. Once you get that clipped in, the harness ran under the fuse box, then clip the fuse box back down, connect your power supply I previously mentioned. Then the part of the fan harness with the two ECM trigger pins will need to be routed to the PCM, and plugged in to the PCM. To to that, you will have to unclip the tabs holding the PCM in place, then undo the two 7mm bolts that hold the harness to the PCM. route your two fan pins in, and you will want to plug the green trigger wire into the BLUE plug pin #42. The blue trigger wire goes to pin #33 in the GREEN plug. A little silicone grease helps a lot when sliding those pins in place. Be very careful removing the PCM harness caps/covers so you don't break them, use a small screwdriver or a pick tool. Now once you get the PCM part out of the way, start running the rest of the fan harness alongside the wire loom that runs from the fuse box down towards the radiator core support. Use some zip ties to secure your fan harness in place to that existing harness. When you get to the bottom of the core support, go towards the passenger side and keep securing the harness alongside the existing factory harness along the bottom of the radiator support. Your fan plugs should line right up in the middle of the radiator if you did everything properly so far. Now take the rest of the harness and keep running it towards the passenger side, and find a good place to ground it on the passenger side frame rail. On the 05-06's, there is a bolt where the harness grounds to the frame just below the frame horn, behind the bumper. On my 2001, my horn is in that area, so I grounded mine using the bolt that holds the horn in place to the frame rail. So now once you get all that done and secured, just plug your fans in (assuming you already mounted your electric fans) and then you are done.

For a little more info and a few pictures, go look at the thread I made when I installed my electric fans. https://www.tahoeyukonforum.com/threads/i-installed-e-fans-on-my-2001.28336/

Excellent info ScottyBoy.

 

[Dan Acosta]

Thanks for the responses! I was able to get the relay box mounted and I ended up routing the wires between the fuse box and fender, I dont know if that is the factory route or between the fuse box and the engine. Either way, looks ok, I did trim the fuse panel housing a little to make for a nicer fit as the wires wrap around.

I am waiting for my tune to get back from Black Bear. I emailed them my files earlier in the week. I have an autocal. I just wanted to get a head start on the wiring since I have some time, and am anxious to get it done.

My biggest concern was probably the debates online about the wiring and earlier models, later models and how the fans would trigger - either from clutch or pressure switch/PCM etc. All the debate left me a little confused. I would prefer to wire as the factory did as possible and it is an 03. I read that the 03s were a little different, so I had some caution in installation.

 

[ScottyBoy]

Thanks for the responses! I was able to get the relay box mounted and I ended up routing the wires between the fuse box and fender, I dont know if that is the factory route or between the fuse box and the engine. Either way, looks ok, I did trim the fuse panel housing a little to make for a nicer fit as the wires wrap around.

I am waiting for my tune to get back from Black Bear. I emailed them my files earlier in the week. I have an autocal. I just wanted to get a head start on the wiring since I have some time, and am anxious to get it done.

My biggest concern was probably the debates online about the wiring and earlier models, later models and how the fans would trigger - either from clutch or pressure switch/PCM etc. All the debate left me a little confused. I would prefer to wire as the factory did as possible and it is an 03. I read that the 03s were a little different, so I had some caution in installation.

As far as the wire routing, they are running UNDER the fuse box from the factory. I explained that in my first post how to lift up the fuse box. As as far as your truck being a 2003, the only thing different from a 99-02 and a 03-04 is the fact that both of the trigger pins will plug into the PCM. A 2003-2004 will wire up EXACTLY like a 05-06, the trigger wires plug into the same exact pins on the PCM.
My 2001 is wired slightly different even though I have a factory harness just like you do. I simply wired an extra relay to my AC compressor wire and that extra relay send a trigger to the blue trigger wire on the OEM fan harness. When I sell OEM harnesses, I will splice in this extra relay for people with a 02 and older, then all they have to do is splice one wire into the AC compressor wire, no other wiring or splicing needed.