Antilock Brake System: Notes

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

The electronically controlled Antilock Brake System (ABS) includes the following components:

1.	Refer to WHEEL SPEED SENSORS (WSS)  .
2.	Refer to SWITCH BANK POD  .
3.	Refer to HILL DESCENT CONTROL (HDC) OR SELEC-SPEED CONTROL (SSC) SWITCH  .
4.	Refer to OCCUPANT RESTRAINT CONTROLLER (ORC)  .
5.	Refer to ELECTRIC PARKING BRAKE (EPB) ACTUATORS  .
6.	Refer to ELECTRIC PARKING BRAKE (EPB) SWITCH  .
7.	Refer to BODY CONTROL MODULE (BCM)  .
8.	Refer to HYDRAULIC CONTROL UNIT (HCU)  .
9.	Refer to BRAKE SYSTEM CONTROL MODULE (BSCM)  .
10.	Refer to INSTRUMENT PANEL CLUSTER (IPC)  .

The electronic components of the ABS system include the Electronic Brake Booster (EBB), WSS, EPB switch, EPB actuators, switch bank pod, HDC/SSC switch, IPC, and BCM.

The EBB is comprised of the Brake System Control Module (BSCM), Brake Pedal Travel Sensor (BPTS), ABS Brake Pressure Sensor, Brake Booster Pressure Sensor and the Hydraulic Control Unit (HCU), which also integrates the master cylinder and brake booster functions. The BSCM and brake fluid reservoir are available for servicing separately from the HCU.

The Electronic Stability Control (ESC) may also be referred to as Electronic Stability Program (ESP) depending on the vehicle model year and configuration. Certain components may also reference ESP, ESC, or use the Traction Control System (TCS) symbol.

OPERATION 

A brief explanation of each subsystem follows.

AUTO PARK BRAKE (APB) 

The APB is designed to automatically apply the EPB as soon as the transmission shifter is put in the PARK position for an auto transmission at standstill condition. This function can be enabled/disabled through the Customer Selectable Features setup menu in the radio.

The APB function can be bypassed even if it is set to ON in the person selection menu. This is accomplished holding the EPB switch in the RELEASE position while shifting from any trans position to PARK.

There are three different ways to reset this bypass:

• Using key cycle from OFF to ON/RUN
• Vehicle begins to accelerate
• With an Auto Park selection cycle OFF then ON using the radio

AUTO VEHICLE HOLD (AVH) 

AVH (sometimes called HOLD-N-GO) is a comfort feature that allows the driver to remove their foot from the brake pedal once the vehicle has come to a stop. The vehicle will be held at a stop for up to a calibrated time by hydraulic braking after which time the electric park brake will engage and continue to hold the vehicle at a stop. Once AVH is released or cancelled, the brake ramp out is smooth and similar to HSA. AVH can be engaged on a slope as well and it will take priority over HSA.

AVH is activated by pressing the HOLD button on the switch bank pod.

Once AVH is active, the driver pressing the brake pedal again will not release the hydraulic pressure being held by AVH. Once AVH is active, this is not considered as having a physical foot on the brake, but the brake pedal is release to the normal, not pressed, position and the vehicle is held with hydraulic brakes alone. The AVH will time out after a calibrated time and the BSCM will activate the EPB.

AVH can keep the vehicle standstill throughout Engine Stop/Start (ESS) events. The BSCM for the AVH feature is not impacted by any state of ESS. However, the Powertrain Control Module (PCM) must know the AVH status, since it replaces a brake pedal pressed signal.

If AVH is restraining the vehicle, the BSCM will set an internal signal to illuminate the brake lights for as long as AVH is restraining the vehicle, whether by AVH or EPB if the AVH has timed out and requested the EPB to hold the vehicle.

AVH will be enabled if:

• A forward gear selected
• Adaptive Cruise Control (ACC) is not engaged
• The driver door is closed
• The driver seatbelt is fastened
• The vehicle is at a standstill
• A minimum braking threshold is exceeded by the driver
• The EPB is not applied
• An Auto Park maneuver is not activated
• No BSCM relevant faults exist

AVH will be cancelled if:

• The automatic transmission gear is moved out of a forward gear
• The EPB is applied using the EPB switch
• The EPB is applied by another means

If the driver door is opened or the driver seatbelt is unbuckled, AVH can remain active and hold the vehicle continuously. However, if both conditions occur, the EPB will be applied and AVH is cancelled. The vehicle will then go into Safe Hold.

AVH will be inhibited if:

• An Auto Park maneuver is activated
• The ACC is engaged and a Stop and Go event is occurring
• The transfer case range changes to LOW or NEUTRAL
• The BSCM detects a brake overheating condition - it will resume after the brakes cool down

BRAKE ASSIST SYSTEM (BAS) 

The BAS is designed to optimize vehicle braking capability during emergency braking maneuvers. The system detects an emergency braking situation by sensing the rate and amount of brake application and then applies optimum pressure to the brakes.

DRAG TORQUE CONTROL 

The Drag Torque Control function tries to avoid locking of the driving axle during throttle-off maneuvers due to engine braking torque. Drag Torque Control is active during throttle-off maneuvers. Drag Torque Control activates when the locking tendency of a driving wheel exceeds the target value.

The BSCM uses the following signals for throttle-off maneuver detection:

• Wheel speed
• Longitudinal acceleration
• Engine torque
• Accelerator pedal position
• Brake system pressure information

The BSCM uses the following signals for locking tendency detection:

• Wheel speed
• Yaw rate

ELECTRIC PARKING BRAKE (EPB) 

The system uses the EPB switch on the left side of the steering column opening cover and two electromechanical actuators, each installed on the rear brake calipers. If either of the actuators ceases to function properly, the actuator that is still working will continue to be used.

Vehicle Movement Operation 

If the vehicle is in motion, pull and hold the button to engage the parking brake for any potential situation requiring Dynamic Braking. Doing this will enable one of three sub-functions of the EPB switch during vehicle movement:

Electronic Control Deceleration (ECD)  - the BSCM will attempt to apply the hydraulic brakes if available.

ECD is activated if the following conditions exist:

• Ignition state is RUN or START
• BSCM is operational
• The EPB is in normal mode - not Maintenance mode
• Vehicle speed is above 3 km/h (2 mph)
• The EPB switch is pressed and is constantly activated

The ECD inhibits operation if any of the following conditions exists:

• The vehicle is in Static or Limp Mode
• The EPB switch is in a Deactivated State - Neutral or Release
• ESC does not work properly (not able to perform the request)
• ESC does not acknowledge the deceleration request
• There are not enough valid wheel speed signals - both rear WSS signals and at least one front WSS signal are required
• The EPB is in Maintenance mode
• Achieved deceleration is less than the calibrated threshold (fallback to ADBF)
• The function is canceled via accelerator pedal usage

Actuator-Dynamic Braking Function (ADBF)  - if the hydraulic brakes are not available, the BSCM will enable the ADBF system, which will operate by increasing the mechanical actuator pressure on the rear caliper pistons and the BSCM will request reduced engine output torque.

The ADBF inhibits operation if any of the following conditions exists:

• The vehicle is in Static or Limp Mode
• The EPB switch is in a Deactivated State - Neutral or Release
• The parking brake is applying or already applied
• There are not enough valid wheel speed signals - both rear WSS signals and at least one front WSS signal are required
• The EPB is in Maintenance mode
• The function is canceled via accelerator pedal usage
• ABS braking is detected

Dynamic Standstill Detection (DSD)  - occurs if the required WSS signal is interrupted or becomes in valid. It is the logic which detects or assumes vehicle movement in the event this situation occurs and the BSCM uses longitudinal G-sensor information to estimate vehicle speed and will apply the hydraulic brakes until the vehicle is at a standstill condition. In order to avoid the risk of vehicle instability by applying the brake fully because of a switch command, the brakes can only be applied with approximately 2 kN (on each side) clamping force on the calipers. In order for this to occur, the following conditions must exist:

• Ignition must be in RUN
• The vehicle's acceleration is greater than the calibrated value
• The EPB is in normal mode - not in Maintenance mode
• Any rear wheel speed signal is invalid or both front wheel speed signals are invalid
• The EPB switch is activated and constantly in APPLY state
• The parking brakes are released (not closing or closed)

If DSD is occurring, the BSCM will activate the stop lights as long as the EPB switch is being activated.

During a dynamic brake event, the BSCM will switch to static apply state of the EPB from dynamic hydraulic brake mode after the vehicle reaches the standstill condition, except where hydraulics are not applicable.

Vehicle Stationary Operation 

If the vehicle is stationary, it is only necessary to pull the switch once to engage the parking brake. To release the parking brake, press the brake pedal, then pull the EPB switch or place the transmission in any gear. The Drive Away Release (DAR) function automatically releases the EPB if the driver seat belt is fastened, a gear is engaged and the accelerator is pressed in order to move the vehicle.

If the brake rotor temperature is higher than 300°C (572°F), the BSCM will re-clamp the EPB at certain time intervals for specific temperatures. If the rotor temperature is 300-399°C (572-750°F), re-clamp will occur after 180 seconds. If the rotor temperature is 400-499°C (752-930°F), re-clamp will occur after 120 seconds and again after 300 seconds. If the rotor temperature is 500°C (932°F) or above, re-clamp will occur after 90 second, then 210 seconds and again after 600 seconds.

The safe hold function occurs when the vehicle speed is lower than 5 km/h (3 mph), the vehicle is not in the PARK  position, and the driver door is ajar will cause the EPB system to apply the parking brake to stop the vehicle safely.

The auto apply function occurs when the vehicle speed is lower than approximately 3 km/h (2 mph) and the automatic transmission is set to PARK  will then cause the EPB system to apply the parking brake automatically.

The status of the EPB functions can be configured in the dedicated radio system menu.

ELECTRONIC BRAKE DISTRIBUTION (EBD) 

The EBD function regulates the rear wheel slip independently during braking to keep the wheels stable and optimize the braking distribution between axles.

EBD allows managing the distribution of the braking torque between the two axles limiting braking pressure to the rear axle to prevent overslip and to avoid vehicle instability.

During tuning phase, the EBD intervention level is defined with the target to reduce possible vehicle drift in straight maneuvers. A correct EBD intervention level minimizes vehicle drift.

EBD is available during braking maneuvers. EBD is activate when the rear axle slip exceeds the target value. If EBD is active, it is switched OFF in case of ABS intervention on the rear axle.

For electronic brake distribution function, the BSCM:

• Calculates target rear slip for both rear wheels
• Estimates the rear brake pressure for both rear wheels
• Calculates the rear pressure target for both rear wheels
• Regulates rear slip

The BSCM uses the following signals for driver braking detection:

• Brake system pressure information
• Brake pedal travel information

The BSCM uses the following internal signals for vehicle speed and wheel slip estimation:

• Vehicle speed estimation
• Wheel slip estimation

ELECTRONIC ROLL MITIGATION (ERM) 

The ERM feature anticipates the potential for wheel lift by monitoring the driver's steering wheel input and the vehicle speed. When the rate of change of the steering wheel angle and vehicle speed are sufficient to potentially cause wheel lift, the appropriate brake will apply and engine power may be reduced to lessen the chance that wheel lift will occur. ERM will only intervene during very severe or evasive driving maneuvers. ERM can only reduce the chance of wheel lift occurring during severe or evasive driving maneuvers. It cannot prevent wheel lift due to other factors such as road condition, leaving the roadway, striking objects or other vehicles.

ERM is available as long as ESC is fully or partially ON, forward drive maneuvering is above a calibrated speed, and the driver steering input threshold is exceeded for the given vehicle speed.

ELECTRONIC STABILITY CONTROL (ESC) 

The ESC system enhances directional control and stability of the vehicle using steering wheel angle, yaw (turning) rate and lateral acceleration sensors (the BSCM uses the yaw rate, lateral acceleration and longitudinal acceleration data from the Occupant Restraint Controller/ORC). Using signals from these sensors, in addition to individual wheel speed sensor signals the ESC corrects for over/under steering of the vehicle by applying the brake of the appropriate wheel to assist in counteracting an over/under steer condition. Engine power may also be reduced to help the vehicle maintain the desired path. Certain components may also reference ESP, ESC, or use the traction control symbol.

HILL DESCENT CONTROL (HDC) 

HDC is a low-speed controller which allows the driver to concentrate on the path of the vehicle while negotiating off-road downhill terrain. HDC will apply hydraulic braking without requiring the driver to apply the brake pedal; HDC activates front and rear brakes while descending a hill to control vehicle speed to a pre-set value. Descent speed is selectable (when the gear shifter is in the drive position) via the transmission gear +/- selectors. HDC is armed by a switch, but the ESC will not actively control braking unless the following conditions are met to activate the feature:

• Ignition is in RUN
• No BSCM faults which prevent HDC functionality
• No Transmission Control Module (TCM) faults which prevent HDC functionality
• The Drivetrain Control Module (DTCM) is not in a failed state
• The driver door is closed
• The driveline is in 4WD LOW
• Vehicle speed is less then 32 km/h (20 mph)
• The EPB is not engaged
• The vehicle is on downhill grade
• The transmission gear is NOT Park

If these conditions are not met while attempting to use the HDC feature, the HDC indicator light will flash ON and OFF. The HDC indicator lamp will be on solid when HDC is enabled. When enabled, HDC senses the terrain and activates when the vehicle is descending a hill. HDC is only intended for low speed off-road driving. The accelerator pedal will override HDC at any time.

HDC is a non-latching feature, that is the feature will not remain available or active from one ignition cycle to the next.

HILL START ASSIST (HSA) 

The HSA system is designed to maintain the level of brake pressure for a short period of time after the brake pedal is released so that the vehicle does not roll on a hill between releasing the brake pedal and applying the accelerator pedal. This function can be enabled/disabled through the Customer Selectable Features setup menu in the radio.

While the HSA feature is holding hydraulic pressure in the brake system, the brake lights will be illuminated. Once the HSA feature releases the hydraulic pressure, the brake lights will be turned OFF.

The following must be true for HSA to activate:

• Vehicle is stopped with the brakes applied
• Vehicle is at an 8% or greater incline
• Gear selection matches the incline direction (forward gear for uphill, reverse for backing uphill)
• Driver door is closed
• EPB is not applied

OFF-ROAD ABS (ORA) ESC 

On deformable surfaces (gravel, sand, and others), a specific Off-Road ABS calibration with higher wheel slip targets may be used to improve the ABS stopping distance. A larger wheel slip will help take advantage of the wedge effect of the deformable surface in front of the tires. Off-Road ABS is automatically enabled if the vehicle has terrain switch setting(s) for deformable surfaces, or it may be enabled if the transfer case is switched to low range. The ORA logic may also be used if the ESC detects a deformable surface based on information from the wheel speed sensors, longitudinal acceleration sensor, and brake torque model. The deeper wheel slip targets used in ORA are dependent on vehicle speed, steering wheel angle, and surface deviation estimation. The ORA logic is not intended to be used on dry or wet asphalt, packed snow, or ice.

The BSCM uses the following signals to help determine if Off-Road ABS is to be activated or not:

• Vehicle speed estimation
• Wheel speed
• SAS angle
• SAS angle type
• Terrain mode selected
• Longitudinal acceleration data
• Brake system pressure data
• 4WD Low status

READY ALERT BRAKING (RAB) 

RAB is a feature that applies very low brake pressure to all calipers to reduce the air gap between discs and pads after a rapid accelerator pedal release is detected. This feature provides a firm confident pedal feel and optimal stopping distance in the case of rapid accelerator release.

RAB is always available but must has the ability to be enabled or disabled based on ESC mode or drive style selection. This is determined by the ESC program. RAB becomes active when vehicle speed reaches the threshold (RAB_SPEED) and when a fast gas pedal release is identified.

RAIN BRAKE SUPPORT (RBS) 

The RBS function supports braking performance under wet conditions. After enable conditions are met, the dry braking is applied whereby the brakes on the front or both axles are activated for a limited time with a very low brake pressure, not perceptible by the driver. The pressure is gently increased and reduced again.

The RBS feature removes the water film that builds up between the pads and the rotors when driving in wet conditions. When the windshield wipers are active, this feature applies a very low brake pressure to all calipers periodically. This maintains a firm, confident brake pedal feel and optimal stopping distance in wet conditions. The disc wiping function is only available under full ESC function. Every fault that causes a partial or full shut-down of the vehicle control function also requires the disc wiping function to shut down.

An active pressure build-up takes place for a predetermined amount of time if the following conditions are fulfilled at the same time:

• Vehicle speed
• Wipers are moving
• Accelerator pedal input
• Lateral acceleration
• Brakes are not being applied by the driver or autonomously
• No other BSCM control features can be active

SAFE HOLD 

The Safe Hold function is to hold the vehicle safely in a standstill condition to prevent unintended vehicle movement. The Safe Hold function is available with or without ESS.

For Safe Hold to be enabled, the following must be true for one of four methods:

Method One

• Ignition must be in RUN
• The vehicle is in static mode - stopped
• The EPB is in normal mode - not Maintenance mode
• The EPB is released
• The EPB switch should be in the NEUTRAL state
• The transfer case is NOT in 4LO or Neutral
• The transmission position is anything but Park
• The accelerator pedal position must be "released" - no pedal input by driver
• The driver door must be open
• The driver seat belt must be unlatched
• The brake pedal not pressed

Method Two

• Ignition must be in RUN
• The vehicle is in static mode - stopped
• The EPB is in normal mode - not Maintenance mode
• The EPB is released
• The EPB switch should be in the NEUTRAL state
• The transfer case is NOT in 4LO or Neutral
• The transmission position is anything but Park
• The accelerator pedal position must be "released" - no pedal input by driver
• The driver door must be open
• The driver seat belt must be unlatched OR the brake pedal not pressed

Method Three

• The hood is open
• The transmission position is anything but Park

Method Four

• Ignition must be in RUN
• The vehicle is in static mode - stopped
• The EPB is in normal mode - not Maintenance mode
• The EPB is released
• The ESS request to shift to park

When all above conditions are met by any of the four methods, the last condition present will trigger the Safe Hold activation and the parking brake is applied by EPB. Once the parking brake is activated by Safe Hold, the parking brake can only be released by the Static Switch Release (SSR) function.

SELEC-SPEED CONTROL (SSC) 

SSC system is a low-speed controller that embraces all of the functions of HDC, but adds engine torque capability to the equation for vehicle speed latching ability in order to be able to maintain the selected vehicle speed even if the vehicle encounters a minor obstruction, such as a rock in front of a wheel. This forward driving momentum also allows the driver to concentrate on the path of the vehicle while negotiating off-road terrain. SSC will apply hydraulic braking without requiring the driver to apply the brake pedal and apply engine torque if a minor wheel obstacle impedes vehicle progress. SSC activates front and rear brakes while descending or ascending a hill to control vehicle speed to a pre-set value and activates engine torque to preserve forward motion. Vehicle speed is selectable (when the gear shifter is in the drive position) via the transmission gear +/- selectors. SSC is armed by a switch, but the ESC will not actively control braking or engine torque unless the following conditions are met to activate the feature:

• Ignition is in RUN
• No BSCM faults which prevent SSC functionality
• No Transmission Control Module (TCM) faults which prevent HDC functionality
• The Drivetrain Control Module (DTCM) is not in a failed state
• The driver door is closed
• The driveline is in 4WD LOW
• Vehicle speed is less then 32 km/h (20 mph)
• The EPB is not engaged
• The transmission gear is NOT Park

If these conditions are not met while attempting to use the SSC feature, the SSC indicator light will flash ON and OFF. The SSC indicator lamp will be on solid when SSC is enabled. When enabled, SSC senses the terrain and activates when the SSC switch is activated. SSC is only intended for low speed off-road driving. The accelerator pedal will override SSC at any time.

SSC is a non-latching feature, that is the feature will not remain available or active from one ignition cycle to the next.

STATIC SWITCH RELEASE (SSR) 

The SSR function is used to release the parking brake in order to liberate the vehicle, due to a driver request on the EPB switch.

SSR activates when:

• The vehicle is in static mode - stopped
• The EPB is in normal mode - not Maintenance mode
• The EPB is released
• The brake pedal is pressed
• Battery voltage check is passed
• There is no fault present that would inhibit EPB function

TRACTION CONTROL SYSTEM (TCS) 

The TCS system (also referred to as ESC) monitors the amount of wheel spin of each of the driven wheels. If wheel spin is detected, brake pressure is applied to the slipping wheel(s) to provide enhanced acceleration and stability. Engine torque manipulation is also used to reduce wheel spin.

The TCS can be deactivated using the ESC/TCS OFF button in the switch bank pod which sends its signals on a Local Interface Network (LIN) data bus. TCS effects can also be modified by the mode that is activated on the Terrain Select Switch or the 4WD LOW/HOLD switch, depending on whether the transfer case is in 4WD HI or LOW. If in 4WD LOW, the TCS defaults to OFF and cannot be activated.

On RWD models, the TCS is ON by default, but can be deactivated with the ESC/TCS OFF button in the switch bank pod. In Sport mode, the TCS is ON by default but can be deactivated with the ESC/TCS OFF button.

When Speed Control is activated and the TCS has been deactivated or is in a partial OFF mode, the ESC will return the TCS to full-ON. The ESC state indicators will continue to indicate the ESC mode that was requested by the customer during this re-engagement condition. The BSCM will return to this previously selected mode once speed control is no longer active or when speed control is overridden by the driver.

TRAILER SWAY CONTROL (TSC) 

Trailer Sway Control (TSC) detects when a vehicle and trailer combination starts oscillating as the trailer will cause yaw oscillation of the towing vehicle (ESP sensors). There are no supplementary sensors on the trailer or trailer coupling device. This means that TSC is essentially a stabilizing device for the towing vehicle. When an oscillation motion has been detected, the vehicle/trailer combination is stabilized by means of alternate brake pressure build-up on the front axle, and also on the rear axle as necessary. In addition to this pressure build-up, the vehicle is decelerated by means of a superimposed brake pressure build-up on all wheels. If additional swinging is detected, the deceleration intervention is increased. The deceleration intervention is accompanied by a reduction in engine torque. The TSC does not change the critical speed of the vehicle/trailer combination.

If increasing oscillation of the towing vehicle is accurately detected on the basis of the target versus actual yaw rate comparison, the intervention must occur as quickly as possible. Only the ESP sensors in the vehicle are used.

In order to reduce the oscillation motion of the towing vehicle, two things happen. The brake pressure is built up alternately on the front axle (and optionally on the rear axle as well) and is synchronized with the vibration characteristics. This is accompanied by superimposed, regulated deceleration on all wheels. For this purpose, the engine torque may be reduced to a minimum level of zero torque in order to prevent the "Engine versus brake" situation from arising. The maximum drag torque may also be used.

YAW MOMENTUM CONTROL (YMC) 

The YMC function (sometimes referred to as Cornering Brake Control/CBC) reduces the oversteer tendency of the vehicle during braking in a curve, without ABS intervention, providing anti-yaw momentum by reducing the rear inner wheel pressure.

YMC is available during braking in curve maneuvers. YMC is not available when an ABS function is active. YMC is active when a vehicle oversteer tendency is detected.

The BSCM system differentiates the rear brake pressure to apply anti-yaw momentum to the vehicle through the reduction of the inner brake.

The BSCM uses the following signals, gated from the BCM, for driver braking detection:

• Brake system pressure information
• Brake pedal travel information

The BSCM uses the following internal signal for vehicle speed estimation:

• Vehicle speed estimation

The BSCM uses the following signals for yaw rate target calculation:

• Vehicle speed estimation
• Lateral acceleration
• Steering angle

EPB MENU MODES 

In-Plant and Emissions Rolls Development (ERD) Mode 

The EPB has an In-Plant Mode and Emissions Rolls Development Mode (ERD) where only static EPB switch Apply/Release functions are available along with only text messages related to these two functions activated.

Inspection Mode 

The Inspection Function allows the EPB system to be tested for certain markets during the required Vehicle Inspection Mode. It automatically detects the tester using wheel speed inputs and runs an apply routine that exercises the EPB for testing. The BSCM detects the vehicle conditions autonomously. If the Inspection Function is canceled or finished, the parking brakes will be released.

The parking brakes will build up a minimum clamp force when applying the EPB switch the first time and the EPB warning light in the IPC will illuminate continuously. Two different methods of increasing the clamp force are available, depending on the usage of the switch:

• The switch can be pulled to the Apply position for the first clamp force step, then released. Each consecutive EPB switch apply will step up the clamp force (executed immediately) until full clamp is achieved.
• If the EPB switch is held in Apply continuously, the function steps up the clamp force every 3 seconds for at least four steps. After the last apply step is reached, a final step will fully apply the parking brakes.

After the last apply step is reached for either method, a final step will fully apply the parking brakes. The parking brakes will be released before radio function exit.

Inspection Function mode is activated/deactivated through the radio menus. The following conditions must exist:

• Ignition in RUN
• All wheel speeds are valid
• Both front wheel speeds are zero
• Rear wheel speeds are within Min/Max tolerance
• EPB released
• No EPB faults present
• Transmission in neutral
• Throttle not applied

Inspection Function mode will be inhibited if the following conditions exist:

• Ignition is turned OFF
• One or more wheel speeds become invalid for more than 1 second
• Front wheel speeds become greater then 1 km/h (1 mph) for more than 1 second
• Rear wheel speeds become out of range for more than 1 second
• Throttle is applied
• Transmission is no longer in Neutral

Maintenance Mode 

Maintenance mode allows the EPB spindle nuts to be driven to the spindle beginning. This permits the caliper piston to be pushed into the caliper bore enabling the brake pads to be changed or to perform other caliper service.

Maintenance mode is activated through the radio menus. The following conditions must exist:

• Vehicle stopped
• Ignition in RUN
• EPB released
• EPB switch is not activated
• Brake pedal not pressed

Maintenance mode will be inhibited and the associated message will be displayed for 5 seconds on the radio screen if the following conditions exist:

• Vehicle in motion - Maintenance Mode is not available while vehicle is in motion. 
• Transmission in D/R/L instead of Park/Neutral - Maintenance Mode is not available. Vehicle must be in PARK or Neutral. 
• EPB applied - Maintenance Mode is not available. Release Park Brake. 
• Brake pedal pressed - Maintenance Mode is not available when brake pedal is pressed. 
• EPB switch is activated
• The EPB already in Maintenance mode

To exit Maintenance mode and return the vehicle to normal operating mode, the following conditions must met:

• Vehicle stopped
• Ignition in RUN
• EPB released
• Brake pedal pressed
• EPB switch is activated