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Home >> GMC >> 2024 >> Terrain SLT, FWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Hydraulic Brakes >> Description and Operation >> Brake Assist System Description and Operation >> Shutdown Test

Shutdown Test

The brake master cylinder performs a self-test 2 minutes after ignition off. The self-test consists of an internal hydraulic test of the brake master cylinder and an external hydraulic compliance test and hydraulic leak test of the brake lines and calipers. The brake master cylinder will take the appropriate actions based on the test results at the next startup. The self-test will not run again until the vehicle has been driven 0.804 Km (0.5 mile), 40.23 kph (25 mph) minimum.

Brake Assist Operating Mode  Description  Vehicle Braking Behavior  Vehicle Speed limited to XXX kph/mph  Red Brake Telltale  DIC  Other Displays 
Full Brake Assist
  • - Normal hydraulic brake assist.
  • - Brake pedal travel and force (pressure) measured.
  • - Pedal feel indicates the relation of the pedal travel to the pedal force.
  • - Brake system applies brake pressure to the wheels to achieve deceleration that makes driver effort comfortable.
  • - Pedal feel: Normal (force to travel of brake pedal).
  • - Brake pedal effort to decel: Normal.
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 No No None None
Full Brake Assist with warning
  • - Normal hydraulic brake assist.
  • - Driver warned with DIC message only of detected failure.
  • - There may be a small brake assist or pedal feel degradation depending on if/where the air is in the system or what component is overheated.
  • - Pedal feel: Normal.
  • - Brake pedal effort to deceleration: Normal.
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 No No Service Brake Assist None
Reduced Brake Assist
  • - Normal hydraulic brake assist available
  • - Driver warned with DIC message but due to nature of failure, engineering determined more warning needed.
  • - Brake assist gain reduced in a noticeable fashion at low pedal travel (not alarming).
  • - Full braking available as pedal is depressed further.
  • - Pedal feel: Normal
  • - Brake Pedal effort to decel: More effort required for low decel values (noticeable). Full braking capability for increased effort.
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 No No Service Brake Assist None
Reduced Brake Assist
  • - Normal hydraulic brake assist on 2 wheels.
  • - Performed when brake system detects and isolates a leak in one of the two brake circuits.
  • - Pedal feel: Normal.
  • - Brake pedal effort to deceleration: Same deceleration requires double the effort. Can only achieve 50% deceleration.
  • - Vehicle will pull slightly to the side with the Front Brake active.
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 Yes Yes Brake System Failure XXX kph/mph Top Speed Low Brake Fluid (Potentially) ABS, ESC, and Engine Telltales Service Traction and ESC DIC Vehicle Speed Limited display from ECM
Two Wheel Brake Assist
  • - Normal hydraulic brake assist on 2 wheels.
  • - Performed when brake system detects and isolates a leak in one of the two brake circuits.
  • - Pedal feel: Normal.
  • - Brake pedal effort to deceleration: Same deceleration requires double the effort. Can only achieve 50% deceleration.
  • - Vehicle will pull slightly to the side with the Front Brake active.
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 Yes Yes Brake System Failure XXX kph/mph Top Speed Low Brake Fluid (Potentially) ABS, ESC, and Engine Telltales Service Traction and ESC DIC Vehicle Speed Limited display from ECM
No Brake Assist with Electric Park Brake Assist
  • - Hydraulic brake assist not available.
  • - Brake System uses Electric Park Brake to assist driver braking.
  • - Pedal feel: Slightly stiffer than normal.
  • - Brake pedal effort to deceleration: Onset of braking is similar but more force required to achieve same deceleration compared with Full Brake Assist.
  • - Minimal non linearities in deceleration due to use of Electric Park Brake.
  • - Pedal travel's almost to the floor with high effort.
 Yes Yes Brake System Failure XXX kph/mph Top Speed ABS, ESC, and Engine Telltales Service Traction and ESC DIC Vehicle Speed Limited display from ECM
No Brake Assist (Push Thru)
  • - No hydraulic or Electric Park brake assist available.
  • - Driver pedal force distributes equal pressure to all 4 wheels
  • - Pedal feel: Slightly softer than normal.
  • - Brake pedal effort to deceleration: Onset of braking requires more travel AND more force required to achieve same deceleration compared with No Brake Assist with Electric Park Brake Assist.
  • - Pedal Travel's almost to the floor with high effort.
 Yes Yes Brake System Failure XXX kph/mph Top Speed (Not displayed for full power loss or critical micro failures) ABS, ESC, and Engine Telltales Service Traction and ESC DIC Vehicle Speed Limited display from ECM
Two Wheel No Brake Assist (2 Wheel Push Thru)
  • - Hydraulic brake assist not available.
  • - Brake system applies and releases Electric Park Brake proportional to driver pedal force to assist driver braking.
  • - Pedal feel: Significantly softer than normal.
  • - Brake Pedal effort to deceleration: Onset of braking requires more travel AND more force required to achieve same deceleration compared with No Brake Assist.
  • - Vehicle will pull slightly to the side with the Front Brake active.
  • - Pedal Travel's almost to the floor with high effort.
 Yes Yes Brake System Failure XXX kph/mph Top Speed ABS, ESC, and Engine Telltales Service Traction and ESC DIC Vehicle Speed Limited display from ECM
Brake Fade Detected Level 1
  • - Normal hydraulic brake assist available.
  • - Brakes system estimates brake temps of 500 - 600 deg C.
  • - Driver warned with DIC display.
  • - Brake assist gain reduced in a noticeable fashion at low pedal travel (not alarming).
  • - If brake assist gain was not changed, the brake over-temp would not be as noticeable as on vacuum brake system.
  • - Pedal feel: Normal
  • - Brake Pedal effort to deceleration: Not significantly changed
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 No No Reduce Braking to Avoid Overheating None
Brake Fade Detected Level 2
  • - Same as Level 1 but brake temperature 700 - 900 deg C.
  • - Degradation in brake lining output may become noticeable.
  • - Degradation in response time may become noticeable.
  • - Far better performance than a vacuum system.
  • - Pedal feel: Normal.
  • - Brake Pedal effort to deceleration: Increase in effort required based on temperature of brake which decreases brake pad output.
  • - Pedal Travel restricted to 80 mm due to pedal simulator.
 Yes Yes Brakes Overheated Service Now None
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