Brake pressure application

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 GMC Yukon XL, 2004 GMC Yukon, 2004 Chevrolet Tahoe, 2004 Chevrolet Suburban, and 2004 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The EBCM uses brake pressure application to control traction by transferring torque through the driveline to wheels which are not slipping. The precharge pump motor, ABS pump motor and appropriate valve solenoids are commanded ON and OFF to apply brake pressure to the slipping wheels. Brake pressure application is used in an attempt to maintain equal WSS signals at the driven wheels.

The EBCM does not allow excessive brake pressure application due to the fact that the solenoid coils or the brakes may become overheated, damaging the EBCM or reducing the driver's ability to stop the vehicle. Estimated coil and brake temperatures are determined by a calculation in the EBCM software. Overheated solenoid coils cause all brake pressure application to become disabled and the stability system disabled message to be displayed. Overheated brakes cause brake pressure application during TCS events to disable, yet the VSES remains functional and as long as the engine torque reduction is enabled, there is no indication to the driver when this occurs and no DTC sets. In either case, engine torque reduction is the only function governing front to rear differential speeds within the transfer case on 4 wheel drive vehicles. Also on 4 wheel drive vehicles, if the engine torque reduction is disabled for any reason when brake application disables, the traction off indicator flashes if wheel slip is detected. Any time the traction off indicator is flashing, there is danger of transfer case damage.