vipers5397

Hello all,
I bought the wiring harness from Lexus for my 04 GX 470. Installed in minutes. Put in an adaptor and hooked up some tow lights and nothing. No brake or signal lights. Like there is no power to the harness.

The question is, is there a switch in the truck that needs to be pressed to make the wiring harness hot? or should it be hot, all the time? It's the right part and hooked right up to the adaptors under the truck by the hitch.

Thanks.

Bob GX

My 04 GX came with a short wire harness (packed in a small envelope in the glove box) that installed up under the dash - does that sound like the harness you are talking about, or was yours an under-the-car affair?

I think the wiring harness to the back came with my GX, but it had the 'tow prep' package from the factory - do you know how yours was originally equipped?

vipers5397

I bought the lexus hitch a few months back and installed that, but only now remembered I needed the wiring harness still. So I got that from lexus. It plugs in two a couple of adaptors under the rear of the truck, and mounts to the hitch. That gives me the 7 pin plug. I plug in some tow lights that I know work, my brother uses them on his truck, and nothing, no brake lights or signal lights. So, should that be hot all the time and no switch somewhere in the GX470 to make the harness hot or off?

LexusBob

Maybe a blown fuse?

vipers5397

LOL. I will punch myself if that what it turns out to be. I'll check them when I get home. I only had time to install and test it yesterday after work. So that is my excuse for not checking the fuses yet .

So it should be hot all the time, right? After fuses, I'll grap the multi meter and see if there is any juice going to the harness lines with the emergency lights going.

vipers5397

Fuses check out fine. Would have been cool if that was it. I went through the who gx and could not find a switch there, or in the manuel, so it should be working. The test using the multi meter shows no current on any of the contacts, but I cannot see why that would be now that I know there is a switch or button for that function.


Any other ideas?

LexusTech

There should be a towing-related relay or two in an underhood fusebox. If they're missing,there's another towing module that has to be installed [along with said missing relay(s)],which I believe is behind the left rear trunk panel.

vipers5397

Thanks LexusTech. That has to be my issue. With that I looked for other posts and found one on lexusowners that confirmed it. Does anyone have the part numbers for these two relays. and where does the fuse box relay go? Under the fuse? The two relays that are needed, one for the underhood fuse box and other for the tow converter box behind the rear taillamp.


"

Since the vehicle didn't come with the tow prep, he's actually missing the relays. Two relays are needed for the underhood fuse box and one for the tow converter box which I believe is in the rear under the tail lamp .

When I did mine (same circumstances), I had to pop one relay in the from box and one behind the tail light (see the photo, the relay is the green box).

A lot of people will tell you that all you need is the relay under the hood, but they rear relay is key. Why? because if you plugged the wiring harness in under the truck, by the spare tire and the relay under the hood, but not the green relay, a volt meter will show weak current when you check continuity at the harness. The green relay is available via mail order at Sewell Lexus.

Photo Attached.

Good luck!

Joe



"

vipers5397

I found the part numbers for one of the relays(had to sub to TIS) and the tow brake controller. I don't know what that looks like, but based on the location on the diagram I have, I think that is there:

T13 Towing Converter Relay 90980–11535

T 8 Towing Brake Controller 90980–11603

I'll post the part number for the other Tow Tail Lamp relay when I find it. If anyone else has that, please post it.

Thanks.

phunboy

Can you provide a photo of the rear tow converter relay or where it's located? I installed the 2 relays up front under the hood. It looks like I cannot get the brake lights and blinkers to function without the rear relay. Help is much appreciated!!

eddyprice

Here is a link that shows the rear tow relay is installed by the driver's tail light. Access is inside the rear trim panel.

http://us.lexusownersclub.com/forums...howtopic=37609

I am also setting up my vehicle to tow - it is a 7/2004 build that came with the tow prep pkg, but apparently does not have the relays. When I hooked up the trailer to the existing 7 wire connection I got no trailer light power with the vehicle light on.

I'm interested to learn how it goes for you. I'll be setting mine up in the next day or two.

eddyprice

phunboy, where do the front relays install? Thx.

phunboy

the front relays install in the front fuse box under the hood. There will be a small auxillary panel next to the fuse box, closest to the firewall. It supports 2 Bosch-type SPDT relays.

mann777

To my knowledge the GX do not have Tow hitch relay as seperate unit, these are controlled by the Back up lamp Relay. Becoz the towing brake controller which is part of the package once installed on the GX. All you need is have them connected to the junction box.

Oregonstit

the photo is no longer attached. Anyone have a pic of the front relays (2) position? I see part number for front elsewhere in this thread. The rear part number is still a mystery. But I think we’ve had good description on where rear relay located. After being so proud of myself for getting the Drawtite hitch on...dead wire harness was a buzz kill.