Trailer Brakes: Description and Operation
Trailer Brake Controls Description and Operation
Some trucks less than 3900 Kg (8600 lb) GVW with a gasoline engine may be equipped with a Trailer Brake Control Module (TBCM) or a combination Fuel Pump/Trailer Brake Control Module (FTCM) system for electric trailer brakes. Some trucks greater than or equal to 3900 Kg (8600 lb) GVW may be equipped with a integrated Trailer Brake Control Module (TBCM) system for electric trailer brakes. The power output to the trailer brakes is based on the amount of brake pressure being applied in the vehicle's brake system. The available power output to the trailer brakes can be adjusted to a wide range of trailering situations.
Note:
Connecting a trailer that is not compatible with the trailer brake system may result in reduced or complete loss of trailer braking. There may be an increase in stopping distance or trailer instability which could result in personal injury or damage to your vehicle, trailer, or other property. An aftermarket controller may be available for use with trailers with surge, air or electric-over-hydraulic trailer brake systems. To determine the type of brakes on your trailer and the availability of controllers, check with your trailer manufacturer or dealer. Do not power-up an aftermarket controller with the factory brake controller at the same time.
The vehicle is equipped with the following trailer braking components:
* Manual Trailer Brake Apply
* Trailer Gain Adjustment
* Trailer Brake Control Panel
* Trailer Brake Driver Information Center Display
The Trailer Brake Control Module (TBCM) or a combination Fuel Pump/Trailer Brake Control Module (FTCM) can support up to a maximum of 4 axles with electric trailer brakes (8 brake magnets).
Manual Trailer Brake Apply
The Manual Trailer Brake Apply Lever is located on the Trailer Brake Control Panel, and is used to apply the trailer's electric brakes independent of your vehicle's brakes. This lever is used in the Trailer Gain Adjustment Procedure to properly adjust the power output to the trailer brakes. Sliding the lever to the left will apply only the trailer brakes. The power output to the trailer is indicated in the Trailer Brake Display Page in the Driver Information Center. If your vehicle's service brakes are applied while using the Manual Trailer Brake Apply Lever, the trailer output power will be the greater of the two.
The trailer and the vehicle's brake lamps will come on when either vehicle braking or manual trailer brakes are applied.
Trailer Gain Adjustment
Trailer Gain should be set for a specific trailering condition, and must be adjusted any time vehicle loading, trailer loading or road surface conditions change.
Setting the Trailer Gain properly is needed for the best trailer stopping performance. A trailer that is over-gained may result in locked trailer brakes. A trailer that is under-gained may result in not enough trailer braking. Both of these conditions may result in poorer stopping and stability of the vehicle and trailer.
After the electrical connection is made to a trailer equipped with electric brakes, the TRAILER CONNECTED message will be momentarily displayed on the Driver Information Center. The Trailer Brake Display Page will appear on the Driver Information Center showing TRAILER GAIN and OUTPUT, after all vehicle related service messages are acknowledged by the driver. The dashed lines in the TRAILER OUTPUT display signifies a disconnected trailer or trailer brake fault condition, and will disappear only when the fault condition is not present.
Trailer Gain Adjustment
* Adjust trailer gain in 0.5 step increments up to 10 gain setting by using the gain adjustment +/- buttons on the trailer brake control panel switch. Pressing and holding a gain button will cause the trailer gain to continuously increment or decrement. To turn the output to the trailer off, set the gain to zero.
* Drive the tow vehicle and trailer combination on a level road surface representative of the towing condition, and free of traffic at approximately 32-40 km/h (20-25 mph) and fully apply the manual trailer brake apply lever mechanism located on the trailer brake control panel switch. Adjusting trailer gain at slower speeds may result in an incorrect gain setting.
* Adjust the trailer gain to just below the threshold of trailer wheel lock-up. Important trailer wheel lock-up may not occur if towing a heavily loaded trailer. In this case, adjust the trailer gain to the highest allowable setting for the towing condition.
Trailer Brake Control Panel
Important:
Re-adjust trailer gain any time tow vehicle and trailer loading or road surface conditions change or if you notice trailer wheel lock-up at any time while you are towing.
The trailer brake system has a control panel with the trailer gain and manual apply switches, and is located on the instrument panel to the left of the steering column. See Instrument Panel Overview for more information on location. The control panel and switches allows you to adjust the amount of output, referred to as trailer gain, available to the electric trailer brakes and allows you to manually apply the trailer brakes. The Trailer Brake Control Panel, and switches is used along with the Trailer Brake Display Page on the Driver Information Center to adjust and display power output to the trailer brakes.
Hill Start Assist and Trailer Sway Control (Heavy Duty Pick-up ONLY)
Hill Start Assist
The hill start assist allows the driver to launch the vehicle without a roll back while the driver is moving there foot from the brake pedal to the accelerator pedal, refer to Hill Start Assist in ABS Description and Operation (Without JL4) Description and OperationABS Description and Operation (With JL4) Description and Operation.
Trailer Sway Control
The trailer sway control can detect the vehicle yaw instability, caused by an attached trailer, refer to Trailer Sway Control in ABS Description and Operation (Without JL4) Description and OperationABS Description and Operation (With JL4) Description and Operation.
Driver Information Indicators and Messages
The following indicators are used to inform the driver of several different factors.
TRAILER CONNECTED
This message will be briefly displayed when a trailer with electric brakes is first connected to the vehicle. This message will automatically turn off in about ten seconds. The driver can also acknowledge this message before it automatically turns off.
CHECK TRAILER WIRING and TRAILER NOT CONNECTED
This message will be displayed if:
* The system detects a trailer with electric brakes is connected to the vehicle, and then the trailer harness becomes disconnected from the vehicle. If a trailer connection is made initially and the vehicle or trailer wiring connections is not correct the TRAILER NOT CONNECTED message will be displayed during the ignition key up as if there is no trailer connected.
* The trailer connection is recognized initially and then a disconnect occurs while the vehicle is stationary, this message will automatically turn off in about thirty seconds. This message will also turn off if the driver acknowledges this message off or if the trailer harness is reconnected.
* A disconnect of the trailer wiring harness occurs while the vehicle is moving, the CHECK TRAILER WIRING message will continue until the ignition is turned off. This message will also turn off if the driver acknowledges this message off or if the trailer harness is re-connected or repairs are completed.
* There is an electrical fault in the wiring to the electric trailer brakes. The CHECK TRAILER WIRING message will continue as long as there is an electrical fault in the trailer wiring. This message will also turn off if the driver acknowledges this message off.
* A poor connection at the 7-way connector may cause the CHECK TRAILER WIRING message. Some aftermarket 7-way trailer side connector adapters or plugs may cause deformation or excessive wear to the vehicles trailer terminals. It is recommended that you use an OEM or Pollak Heavy Duty 7-Way Trailer Side Connector Adapter.
SERVICE TRAILER BRAKE SYSTEM
This message will be displayed when there is a problem with the trailer brake control system. If this message persists over multiple ignition cycles there is a concern with the trailer brake system. Take your vehicle to an authorized GM dealer to have the trailer brake system diagnosed and repaired.
TRAILER GAIN and OUTPUT Display
This display menu can be accessed by scrolling through the Driver Information Center menu, or any time the trailer gain +/- button is depressed, or the manual trailer brake apply lever is actuated. The trailer gain display is 0 to 10 in 0.5 step increments, and indicates the current user setting of the trailer output gain. The trailer output is 0 to 10 bars in 1 bar increments, and indicates the output power provided to the trailer brakes, relative to the gain setting.