NEED HELP Brake Controller

byteme

Member
hooking up a reese controller its very hard to read the specs on the wires from under the dash almost like they were drunk on a friday , I hooked it up the way believed was right but only got the blink light on the control when brakes applied .??Any help appreciated
 

Mooseman

Moderator
Double check the trailer connector. When mine isn't all the way in, I don't get the C on my Prodigy's display and doesn't do anything. You'll know it's in right when you can't pull it out without lifting the cover.
 

Reprise

Lifetime VIP Supporter
IIRC, the wire colors were almost directly opposite on the Envoy's harness, compared to my TBC (also a Prodigy).

Here's the color layout (you should have found 4 wires tucked up near the firewall, on the LH side, after you remove the panels under the steering wheel). IIRC, there's a piece of blue tape binding them together, and there's a white label that details the color layout):

Red - Battery +
Dark Blue - Trailer brakes
Black - Ground
Light Blue - Trailer Stop lamps

If you've got them connected correctly to your TBC (and assuming you connected the thicker red wire with ring terminal to the post underhood, adjacent to the fuse box), the next place to check is the 7-way connector at the back of the truck. Get a multimeter, and check for voltage on each of the pins applicable to their function.

(On my Envoy, the brake light pin was corroded in the connector; it took a few minutes to figure out why all the lights *except* the brake lamps) on the trailer were working. Got it working enough to get the trailer home; I then had to take the connector apart and remove the rest of the corrosion on that pin.) Problem solved.

As an aside, It's also a good idea to carry a small tube of dielectric grease and put that on the connector pins every few times you connect it to the trailer's umbilical cord. Permatex has a small (1/4oz ?) size you can get at your local auto parts store.
 
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byteme

Member
Double check the trailer connector. When mine isn't all the way in, I don't get the C on my Prodigy's display and doesn't do anything. You'll know it's in right when you can't pull it out without lifting the cover.
Our connecter locks to the plug so im sure it sin but will test again thanks
 
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byteme

Member
IIRC, the wire colors were almost directly opposite on the Envoy's harness, compared to my TBC (also a Prodigy).

Here's the color layout (you should have found 4 wires tucked up near the firewall, on the LH side, after you remove the panels under the steering wheel). IIRC, there's a piece of blue tape binding them together, and there's a white label that details the color layout):

Red - Battery +
Dark Blue - Trailer brakes
Black - Ground
Light Blue - Trailer Stop lamps

If you've got them connected correctly to your TBC (and assuming you connected the thicker red wire with ring terminal to the post underhood, adjacent to the fuse box), the next place to check is the 7-way connector at the back of the truck. Get a multimeter, and check for voltage on each of the pins applicable to their function.

(On my Envoy, the brake light pin was corroded in the connector; it took a few minutes to figure out why all the lights *except* the brake lamps) on the trailer were working. Got it working enough to get the trailer home; I then had to take the connector apart and remove the rest of the corrosion on that pin.) Problem solved.

As an aside, It's also a good idea to carry a small tube of dielectric grease and put that on the connector pins every few times you connect it to the trailer's umbilical cord. Permatex has a small (1/4oz ?) size you can get at your local auto parts store.
Is that power wire at the fuse panel not attached from the factory ??? I have power to the unit will check the colors on sunday when we get back from the car show in Bothwell , thanks
 

Reprise

Lifetime VIP Supporter
The GM plant left it detached at the factory, theory being that because not everyone tows, they leave it disconnected by default. But that's what sends the power through the trailer harness / provides +12V to charge your trailer battery while driving. You may find it tucked away, but it's there. Do a search (on Google) for which post to connect it to. Just make sure you DON'T connect it to the posts that house that 125A 'megafuse'. Since I'm talking about it, here's a pic I found showing the three posts. The wire goes on that 'vacant' one (bottom of the three on RH side in pic below)

90411
(pic is from a TBSS, but all are similar)

IIRC, there's also a fuse or two that needs to be checked to make sure it / they are in their proper slots in the fuse block, too. As I recall, I had the fuses present - but I did have to connect the ring terminal.

Supposedly, the terminal is to be disconnected when finished towing -- but I leave mine connected full-time, even though I really don't tow with the Envoy anymore (got a Sierra to take over the tow duties). I should probably disconnect it, TBH. Point is, I don't find that it drains my battery, and I sometimes go several days between starts on the vehicle. YMMV.
 

Mooseman

Moderator
For even more clarity:
Red Wire (The disconnected ring connector near battery/underhood fuse box)

You can leave it connected. It won't do anything with nothing connected to the trailer plug. Even with a trailer plugged in, unless you've got something connected to that particular lug in it, it won't do anything. Absolutely no logic to why the factory would leave it disconnected.
 
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byteme

Member
For even more clarity:
Red Wire (The disconnected ring connector near battery/underhood fuse box)
Thanks ill find out in a hour much appreciated

The GM plant left it detached at the factory, theory being that because not everyone tows, they leave it disconnected by default. But that's what sends the power through the trailer harness / provides +12V to charge your trailer battery while driving. You may find it tucked away, but it's there. Do a search (on Google) for which post to connect it to. Just make sure you DON'T connect it to the posts that house that 125A 'megafuse'. Since I'm talking about it, here's a pic I found showing the three posts. The wire goes on that 'vacant' one (bottom of the three on RH side in pic below)
Thanks I saw something about this red wire on a utube video and they werent sure what it did ,
thanks
 
Last edited by a moderator:
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byteme

Member
For even more clarity:
Red Wire (The disconnected ring connector near battery/underhood fuse box)

You can leave it connected. It won't do anything with nothing connected to the trailer plug. Even with a trailer plugged in, unless you've got something connected to that particular lug in it, it won't do anything. Absolutely no logic to why the factory would leave it disconnected.
now all i need to do is find a nut for the terminal but thanks yes it was off just laying there
 
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byteme

Member
But this has absolutely nothing to do with the brake controller or brakes.
so i figured that out as i still have no trailer brakes just the stupid dot and teh power wirte under the hood is for charging the battery in the trailer so ill get my meter out and scratch my head for a bit
 

Mooseman

Moderator
Pull the connector off the back of the 7 way plug under the truck. I had a ground issue and it was a corroded connector inside the plug.
 

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