Factory integrated brake controller not recognizing trailer.

[dkad260]

2012 XL Denali with OE controller, will not display the trailer is connected, I tested this on a 2nd trailer also.

Trailer lights, signals, and brake lights work, no corrosion on either side of the 7-pin connector.

I removed the kick panel and the controller is connected, also the controller illuminates when headlights are on.

I do have the JL1 RPO code

Fuse #6 is good.

No codes

Pressing the +/- buttons or sliding the lever does not display anything.

Would the relay cause this?

 

[dkad260]

Ok, I double checked under the hood, I see a red wire wrapped up outside a wire loom with a ring terminal. I'm assuming that's our mystery GM red wire.

 

[swathdiver]

2012 XL Denali with OE controller, will not display the trailer is connected, I tested this on a 2nd trailer also.

Trailer lights, signals, and brake lights work, no corrosion on either side of the 7-pin connector.

I removed the kick panel and the controller is connected, also the controller illuminates when headlights are on.

I do have the JL1 RPO code

Fuse #6 is good.

No codes

Pressing the +/- buttons or sliding the lever does not display anything.

Would the relay cause this?

If anything is amiss with the trailer brake system it will not connect to anything. If everything checks out, it is possible that the trailer's type of brake system is not compatible.

Reading this again, are you saying that if you move the slider nothing appears on your DIC? It ought to.

The SSR is located right behind the ABS pump. Do you have a bi-directional scan tool to pull chassis codes? That's where the ITBC resides.

 

[swathdiver]

Ok, I double checked under the hood, I see a red wire wrapped up outside a wire loom with a ring terminal. I'm assuming that's our mystery GM red wire.

Hold, on, was this under the brake booster or alongside the fender? If you have JL1, this should have been connected already. Do not connect if an aftermarket controller is attached with the wires from under the dash.

 

[dkad260]

Hold, on, was this under the brake booster or alongside the fender? If you have JL1, this should have been connected already. Do not connect if an aftermarket controller is attached with the wires from under the dash.

I don't have an aftermarket controller, only the original factory integrated.

This is the red wire outside the fuse box on the fender.

 

[swathdiver]

I don't have an aftermarket controller, only the original factory integrated.

This is the red wire outside the fuse box on the fender.

View attachment 376885

OK, that gets connected to the left terminal and you'll be all set then. If you want power to the inside the trailer, the other bundle of wires under the brake booster gets connected to the right terminal. Remember though, even when the truck is off, it is powering the trailer's interior with that wire connected.

 

[Fless]

OK, that gets connected to the left terminal and you'll be all set then. If you want power to the inside the trailer, the other bundle of wires under the brake booster gets connected to the right terminal. Remember though, even when the truck is off, it is powering the trailer's interior with that wire connected.

What do you mean by "left" terminal? The one on the driver's side, or the one on the left as viewed from the front of the truck?

 

[gooffeyguy]

The terminal posts are different size and so are the ring connectors on the ends of the wires and they'll only go on the corresponding terminal post.

When looking at the engine, the wire bundle on the right (between fender and fuse box) goes to the left terminal post, and the wire bundle on the left (under brake booster) goes to the right terminal post.

 

[swathdiver]

What do you mean by "left" terminal? The one on the driver's side, or the one on the left as viewed from the front of the truck?

As Tom described it.

 

[dkad260]

Ok, so the wire I pictured was under the brake booster, there is another tucked away next to the fender...that one has the larger terminal.

The pic shows that the larger wire is for an "aftermarket" controller. Is that still the one for the factory ccontroller? I assume not.

 

[dkad260]

Looking back, it sounds like the wire next to the fender with the larger terminal is for the factory integrated brake controller.

With that wire hooked up, I have nothing displayed when the trailer is connected.

 

[dkad260]

Update.

I hooked up the smaller ring terminal by itself and no luck. I removed the small terminal and hooked up the large ring terminal...again, no luck.

I then hooked up both terninals....no luck.

I lightly sanded the terminals to remove any oxidation as well.

 

[swathdiver]

Double check ALL of the fuses and specifically, 1, 3, 6, 25, 63 and 68. If that doesn't get it working, you're going to need a Tech-2 or something similar to test and diagnose this. There is a thread that shows where people live that would be happy to run it on your truck.

Behind the ABS module is the Solid State Relay (SSR), make sure that is plugged in. On the driver's side frame rail is where the ITB module resides, make sure it is connected and consider reseating the connector to make sure corrosion is not a factor.

If there are any Internal Chassis or BCM codes related to this, it will not work either. A basic code reader cannot see these codes.

 

[dkad260]

Thanks, I will check those fuses in the AM, then climb underneath if needed.

I do have a Tech 2 and will double check for any codes.... nothing on the dash or DIC...yet.

Haven't done any troubleshooting with it in regards to the brake controller yet, but will check it out.

 

[swathdiver]

Thanks, I will check those fuses in the AM, then climb underneath if needed.

I do have a Tech 2 and will double check for any codes.... nothing on the dash or DIC...yet.

Haven't done any troubleshooting with it in regards to the brake controller yet, but will check it out.

Awesome, fire up the Tech-2 tomorrow and run some diagnostics.

 

[dkad260]

OK, that gets connected to the left terminal and you'll be all set then. If you want power to the inside the trailer, the other bundle of wires under the brake booster gets connected to the right terminal. Remember though, even when the truck is off, it is powering the trailer's interior with that wire connected.

Just wanted to touch on this for future reference for the sake of L vs R.

The wire under the brake booster has to go on the left terminal viewed from the driver's seat.

The wire next to the fender goes on the right terminal as viewed from the driver's seat.

Again, this was also clarified later as they are different sizes and can only be properly used one way...except the larger ring terminal could mistakenly be placed on both posts.

I have checked all the fuses listed earlier and all are good.

Will keep hunting.

 

[dkad260]

With the Tech 2, I was able to pull these codes, no idea how old they are.

With these current codes, as well as after I cleared them, still no brakes.


I was able to view the "Manual Apply Switch" percentage, and I could watch the values go from 0% to 100% as I moved the slider.

I went to the 7-pin on the rear of the Yukon, hooked my DMM to the ground and trailer brake terminal. I was getting a constant fluctuation from about 3.7 V to 4V. When I moved the slider or pressed the brake pedal, those values didn't change...kept fluctuating.

I checked the trailer's 7-pin connector and all the wires are clean and connected.

 

[swathdiver]

C1118 08

The TBCM detects the user gain switch is applied before the ignition is cycled OFF, and continuously applied for 30 seconds after ignition is cycled to ON.
The TBCM detects the user gain switch is applied continuously for 5 minutes.

Circuit/System Testing​

1. Ignition OFF, disconnect the harness connector at the trailer brake controller switch.
2. Test for less than 5 ohms between the low reference circuit terminal 8 and ground.
   • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the TBCM.
3. Ignition ON, test for 4.8 - 5.2 volts between the 5-volt reference circuit terminal 3 and ground.
   • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
   • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
4. Verify the scan tool Manual Apply Switch parameter is less than 5 percent.
   • If greater than the specified range, test the signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the TBCM.
5. Install a 3A fused jumper wire between the signal circuit terminal 4 and the 5-volt reference circuit terminal 3. Verify the scan tool Manual Apply Switch parameter is greater than 90 percent.
   • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
6. Verify the scan tool Redundant Manual Apply Switch parameter is greater than 90 percent.
   • If less than the specified range, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the TBCM.
7. Install a 3A fused jumper wire between the signal circuit terminal 5 and the 5-volt reference circuit terminal 3. Verify the scan tool Redundant Manual Apply Switch parameter is less than 2 percent.
   • If greater than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
8. Ignition ON, test for 4.8 - 5.2 volts between the signal circuit terminal 6 and ground.
   • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
   • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
9. If all circuits test normal, test or replace the trailer brake controller switch panel.

 

[dkad260]

Thanks!

I'm looking online, not finding it, but does anyone have the pinout for this module?

 

[dkad260]

Not sure if this is correct, but in this pic, between ground (pin B), and Pin C, I have .9 ohms.

Also, is this a relay for the brake controller?