2024 GMC Sierra 1500 Brake Controller: Setup and Gain

The 2024 GMC Sierra 1500 brake controller is GM's factory Integrated Trailer Brake Control (ITBC, option code JL1): a small panel on the dash with gain +/- buttons and a manual apply lever that powers a trailer's electric brakes through the truck's 7-pin connector. You set it by adjusting trailer gain on a 0.0 to 10.0 scale during a low-speed road test, not by picking a number from a chart. Not every 2024 Sierra 1500 has it, and GM has told dealers it can't be retrofitted to trucks built without it, so those trucks need an aftermarket controller instead.

Does Your 2024 Sierra 1500 Have the Factory Controller?

Look on the dash near the steering column for the trailer brake control panel: two gain buttons and a sliding lever. If it isn't there, check the Service Parts Identification label (usually in the glove box) for the option code JL1, which is GM's code for the integrated trailer brake controller.

If your truck doesn't have JL1, don't count on a dealer adding the factory system later. In GM bulletin PIT5828A, filed with NHTSA, GM told dealers that if a 2019-2022 Sierra, Silverado, Tahoe, Yukon or Escalade "does not have the option (RPO JL1), it cannot be added to the vehicle." An earlier bulletin said the same for 2014-2016 trucks. We haven't found a GM document that changes that for 2024, so plan on an aftermarket controller for a non-JL1 truck and confirm with your dealer by VIN.

How the Integrated Controller Works

The ITBC isn't a standalone box bolted under the dash. It's tied into the truck's own brake, antilock brake and StabiliTrak systems, and it only works with the ignition on. A trade breakdown of GM's trailer brake technology on 2014-and-newer GM pickups describes three main parts:

Component	What it does
Trailer brake control switch (dash panel)	Lets the driver set trailer gain and apply the trailer brakes manually
Brake system control module	Decides how much trailer braking to command and sends that request over a dedicated data line
Trailer brake power module (above the spare tire)	Produces the actual brake output voltage that goes to the trailer through the 7-pin connector

Because the truck's brake module is doing the math, braking output follows how hard you press the pedal. That's why the factory controller feels more like a proportional unit than a basic time-delay box.

The manual apply lever

Sliding the lever applies only the trailer brakes. Both the truck's and the trailer's brake lamps come on when you use it. If you press the pedal and use the lever at the same time, the trailer gets whichever output is greater, not the two added together. Output shows on the Trailer Brake Display Page in the Driver Information Center (DIC).

Which Trailer Brakes It Works With

Trailer brake type	Factory ITBC?	Notes
Electric (magnet) drum brakes	Yes	The most common setup on travel trailers and utility trailers
Electric-over-hydraulic (EOH)	Yes, on 2014+ GM trucks with the EOH mode selected	The trailer's pump needs a different output signal; select the brake type as the owner's manual describes
Surge (hydraulic)	Not needed	Surge brakes work off the trailer's own momentum and don't need a controller
Air brakes	No	Need a dedicated aftermarket system

Older GM manuals said the ITBC works only with electric brakes. EOH support came with the later system, so check your own owner's manual before you tow an EOH trailer.

Setting Trailer Gain

Gain decides how much current goes to the trailer brakes for a given amount of pedal or lever input. It adjusts from 0.0 to 10.0 in the DIC, with or without a trailer connected. The factory default is 0.0, which means no output to the trailer, so a new truck or a reset controller won't brake the trailer until you set it.

GM's gain procedure in the owner's manual comes down to this:

1. Make sure the trailer brakes work and the trailer is loaded the way you'll actually tow it.
2. Hook up the trailer and plug in the 7-pin. The DIC should show the trailer as connected and bring up TRAILER GAIN and TRAILER OUTPUT.
3. On a level road with no traffic, drive at about 20-25 mph (32-40 km/h).
4. Slide the manual apply lever all the way over.
5. Adjust gain to just below the point where a trailer wheel locks up (tire squeal or smoke). If the trailer barely slows, raise it and repeat.

Heavily loaded trailers may never reach lockup. In that case GM says to use the highest gain allowed for that towing condition. Run the test again any time the trailer, the load or the road surface changes, and back off gain on wet, icy or gravel roads. For 1500 vs. 2500 differences and what over- and under-gaining feel like, see our Sierra trailer brake gain settings guide.

Warning Messages You May See

The DIC reports trailer brake faults as text messages. Two common ones:

DIC message	What it usually points to
CHECK TRAILER WIRING	An open circuit or high resistance in the trailer brake circuit during the current drive cycle, often a corroded 7-pin, a loose trailer ground or a broken brake wire
SERVICE TRAILER BRAKE SYSTEM	A fault the system can't clear on its own. The trade analysis above links it with code C1114 to a poor trailer ground or a short to power on the brake output wire

Before you blame the truck, check the trailer: clean the 7-pin contacts, look at the trailer's ground to the frame, and look for chafed wire at the tongue and axle. Our guide to the Service Trailer Brake System message goes through the full diagnosis. If you need to stop the warning when you're not towing, see how to turn off the trailer brake system on a GMC Sierra. On older trucks the trailer brake module itself can fail; see replacing the trailer brake control module.

2023 vs. 2024 Sierra 1500: Is the Controller Different?

Both model years belong to the same Sierra 1500 generation that began in 2019, and both use the dash panel, gain procedure and 7-pin connection described above. We haven't found a GM owner's manual or service bulletin that documents a functional change to the ITBC between 2023 and 2024. If you're shopping used, what matters is whether the specific truck has JL1, not which of the two years it is. The setup steps on this page apply to both.

If Your Truck Doesn't Have JL1

An aftermarket electric brake controller is the normal fix. Pick a proportional controller if you tow often or tow heavy. Most mount under the dash and connect with a vehicle-specific plug-in harness instead of spliced wires. Our guide on how to use a GMC trailer brake controller covers the difference between proportional and time-delay controllers. For the 7-pin pinout and wire functions, see GMC trailer brake controller wiring. Before you tow, confirm the trailer weight against your truck's rating; our 2023 Sierra 1500 towing capacity page lists the numbers for this generation.

Frequently Asked Questions

Where is the trailer brake controller on a 2024 GMC Sierra 1500?

On trucks built with the JL1 option, the control panel sits on the dash near the steering column, with gain +/- buttons and a sliding manual apply lever. Gain and output show in the Driver Information Center. If there's no panel and no JL1 code on the glove box label, the truck was built without it.

Can the factory brake controller be added to a Sierra that didn't come with it?

GM has told dealers in NHTSA-filed bulletins that JL1 can't be added to 2014-2016 and 2019-2022 full-size trucks that weren't ordered with it. Plan on an aftermarket controller for a 2024 without JL1 too, and confirm with your dealer by VIN.

What should the gain be set to?

No single number fits every trailer. Set it with the trailer attached by driving at 20-25 mph, fully applying the manual lever, and adjusting to just below the point where a trailer wheel locks. Heavier trailers usually end up at higher settings. Gain at 0.0 means no trailer braking at all.

Does the Sierra's controller work with surge brakes?

Surge brakes don't need a controller, because the trailer's coupler applies them hydraulically as the trailer pushes against the truck. The integrated controller is for electric brakes and, on 2014-and-newer GM trucks, electric-over-hydraulic brakes with the EOH mode selected.