Page 41
EPB (Electronic Park Brake)
The Electronic Park Brake consists of an actuator and the control unit in one housing. It is
able to apply the park brake by CAN request.
Block diagram EPB
40
Page 42
Functional description EPB
The Electronic Park Brake replaces the conventional manual park brake. It can be installed
in the car as an option.
1b
Layout
The module consists of several parts:
1. Actuator
a. Motor
b. Spindle
2. Electronic Control Unit
The force of the motor is distributed to
the spindle via transmission. The spindle
is connected to the brake cable of the
brakes. So turning the motor means
applying or releasing brake torque.
1a
2
The included ECU controls the motor’s torque and speed and therefore the force distributed
to the brakes. This is needed due to the fact that EPB is able to apply brakes percentaged.
Functions
The functions of the EPB can be split into four sections:
1. Manual mode
a. Static apply
b. Static release
c. Dynamic braking
2. Automatic mode
a. Drive away (including hill holder)
3. Service mode
a. Assembly adjustment
b. Normal operation adjustment
c. Maintenance mode
d. Brake test mode
4. Failure mode
Each mode will be explained below.
Static Apply
When the vehicle is in static mode and the driver activates the EPB button, the actuator
must apply the nominal force to the parking brake, which is necessary to hold the loaded
vehicle securely at a slope up to 30%. EPB can be applied in every power state, even if the
key is not in.
41
Page 43
Static Release
This function releases the EPB upon the driver's request. Key must be in power on mode and
brake pedal has to be pressed.
Dynamic braking
When the vehicle is moving and the driver activates the EPB by pulling the button, the
actuator may react in different ways depending on the actual wheel speed. When wheel
speed is over 6 km/h, EBCM will apply brakes with 0.6g. EPB will not apply. As soon as the
driver releases the EPB button, the EBCM stops braking. When wheel speed is below 6 km/h,
EPB will apply 100%.
Drive away
This function releases the EPB during drive off maneuvers. The EPB system allows the driver
to depart without giving any additional command to the EPB system. Drive away function is
triggered by clutch pedal and throttle. The brake torque on the parking brake will be
released in what the driver perceives as a comfortable and convenient way.
It is also possible to use the drive away function on slopes. EPB will hold the car and
automatically release the brake torque when clutch and gas pedal are in a defined position.
The detection of uphill or downhill driving direction is included.
Assembly adjustment
It must be possible to instruct the actuator to do the assembly stroke and perform 5
apply/release cycles to accommodate for the initial compression of the cable jacket (incl.
calibration).
Normal operation adjustment
EPB motor control definition guarantees a continuous self-adjustment to cable wear.
Service mode
This mode is needed to exchange the brake cable. A full release can be performed, which is
necessary to unhook the cable.
Brake test mode
This mode is used during parking brake efficiency tests on rolling test benches.
Failure mode
EPB is able to handle some failure modes. Here are some examples. For a full list please see
the specs.
o EBCM failed / not available: EPB will take the dynamic brake function as best as
possible.
o Wheel sensors not available during dynamic mode: EPB will use a ramp-up to apply
brake torque.
42
Page 44
Connectors and pin assignment EPB
2500
2500
G
2500
H
J
K
A50
2501
L
2501
M
N
P
R
S
2501
1492
5986
6107
6108
43
0.5
0.5
C40
B40
0.5
A40
4
0.5
0.5
A40
0.5
B40
0.5
0.5
0.5
0.5
0.5
C40
Pigtail Wire Color
E
F
0.5
0.5
Pigtail Wire Gauge
1134
7684
4
0.5
Terminal Plating
C
D
Battery Positive Voltage (VBAT+)
Park Brake Release Switch Voltage Reference
(SW NC Release)
Park Brake Switch Signal (SW NO)
Park Brake Apply Switch Voltage Reference
(SW NC Apply)
R_Termination_1
High Speed GMLAN Serial Data (+) (1) (CANH
1)
High Speed GMLAN Serial Data (+) (2) (CANH
2)
Ground (VBAT-)
Spare Out
High Speed GMLAN Serial Data (-) (2) (CANL
2)
High Speed GMLAN Serial Data (-) (1) (CANL
1)
R_Termination_2
Park Brake Switch Supply Voltage (SW TL NO)
Serial Data Communication Enable (COMM EN)
Park Brake Apply Switch Signal (SW Supply A)
Park Brake Release Switch Signal (SW Supply R)
Shield Group
A40
7683
Circuit Description
Twist Group & Rate
Circuit #
A
B
Minimum Wire
Gauge
Max. Wire
Resistance
Cavity
X1
Page 45
Fuel System Control Module)
The Fuel System Control Module powers the fuel pump by PWM signal and provides fuel
pressure requested by ECM.
Block diagram FSCM
FSCM
FSCM
Serial Data (HS GMLAN)
Batt
Power Supply
Ign
Gnd
PWM Signal (25kHz)
Pressure Request
ECM
Pressure Status
Drivers
Fuel Pump Enable
µC
SSR
Fuel Pump
Liquid Fuel Pressure
Comm. Enable
Functional description FSCM
The Fuel System Control Module is the controller for the fuel pump in the Electronic
Returnless Fuel System ERFS (shown below).
12 V
0V
Vbatt
FSCM
Serial Data
ECM
Fuel Pump Enable
Fuel Pressure
Fuel
Pressure
Sensor
Fuel Tank
Fuel Rail
Check
Valve
M
P
Pressure
Vent Valve
(PVV)
44
Page 46
ERFS is an enhancement of the Mechanical Returnless Fuel System MRFS. MRFS consisted of
less parts and was therefore less complex. The ECM directly drove a relay which activated
the fuel pump. The pump constantly delivered a certain amount of fuel. The pressure
distributed to the fuel rail(s) was regulated by a valve (similar to PVV shown above
concerning position).
The most important change in ERFS is that the fuel pump is no longer driven by a relay, but
by a 25kHz PWM signal. That means, that the fuel pressure can be influenced by FSCM by
changing the duty cycle of the PWM signal. The valve that was needed with ERFS is of no
regulatory importance any more. It is just used as an over pressure security device.
FSCM is responsible for providing the pressure requested by the ECM. To ensure that the
right pressure is provided, FSCM has to control the fuel pump. This is done by a closed loop
including a PID controller. The fuel pressure delivered to the fuel rail(s) is measured by a
sensor. This sensor is connected to the FSCM and therefore gives the FSCM the opportunity
to react on differences between requested and provided fuel pressure. The fuel pump
signal’s duty cycle will be adapted.
FSCM has some other advantages:
• fuel economy improvement through reduced electrical load on alternator
o Eliminates liquid recirculation in fuel tank
o Reduced rail pressure under most operating conditions
• Mitigate hot fuel handling issues through on-demand, increased fuel delivery pressure
• Mitigate fuel injector dynamic range issues on high performance applications
• Enables potential improvement in air/fuel ratio control and emission performance
45
Page 47
Connectors and pin assignment FSCM
46
C
A
A
A
C
A
A
Pigtail Wire Color
Pigtail Wire Gauge
A39
1580
5986
2501
2500
A40
7445
7444
120
B
B
Terminal Plating
15
16
17
21
22
32
36
44
47
Ground (GND1)
Fuel Line Pressure Sensor Low Reference
High Speed GMLAN Serial Data (-) (2)
High Speed GMLAN Serial Data (+) (2)
Fuel Line Pressure Sensor Signal
Fuel Control Enable / Fuel Pump Primary Relay
Control
Run/Crank Ignition 1 Voltage (R_C_1)
Fuel Pump Low Reference
Serial Data Communication Enable
High Speed GMLAN Serial Data (-) (1)
High Speed GMLAN Serial Data (+) (1)
Battery Positive Voltage (SRC1)
Fuel Line Pressure Sensor 5V Reference
Fuel System Control Module Shield
Fuel Pump Supply Voltage
Shield Group
A50
7447
2501
2500
7446
465
Circuit Description
Twist Group & Rate
Circuit #
1
5
6
7
10
13
Minimum Wire
Gauge
Max. Wire
Resistance
Cavity
X1
Page 48
IPB (Image Processing Bundle)
The Image Processing Bundle combines two systems in one box:
• LDW (Lane Departure Warning)
• TSM (Traffic Sign Memory)
The Lane Departure Warning is a vision-based lane detection
system capable of warning the driver in case of inadvertent lane
change.
Traffic Sign Memory is able to determine traffic signs and displays them in the instrument
cluster.
Block diagram IPB
IPB
Batt
3
integrated
Image
Low Speed CAN
7,8
Ground
1,2,
5,9
Camera
Processing
Bundle
10
LDW
Switch
9
4
Functional description IPB
The Image Processing Bundle provides an integrated camera module, located on the
windshield behind rearview mirror. It is therefore able to see lanes and traffic signs.
The pictures taken from the camera are sent through a signal processing unit. After that,
LDW and TSM algorithms are performed. Now the module has determined if an inadvertent
lane change is performed or if the driver is to pass a traffic sign.
Functional description LDW
LDW needs some conditions to be fulfilled for being able
to work properly:
• Vehicle speed greater than 55 km/h
• camera detecting at least one good lane marking
• clean windshield
47
Page 49
• good environmental conditions (i.e. no rain, snow, direct sunlight, shadows)
If LDW is active, a green telltale will indicate this state. Within an alert, this telltale will
change its color to amber and start flashing. In addition, a chime sound is activated.
The whole system is inhibited with one of three methods:
• Turn Signals
• Over Steering
• Significant Acceleration
• Break activation
The telltale will turned off if no lane marking could be detected.
Functional description TSM
TSM is specified to work in Europe only. It is actually able to recognize the
signs shown on the right.
Speed limits
For proper working, some conditions have to be fulfilled:
• clean windshield
• clean signs (i.e. not snow-covered, dirty)
• good environmental conditions (i.e. no rain, snow, direct
sunlight, shadows)
48
No passing
Page 50
Connectors and pin assignment IPB
X1
1
2
3
4
A51
A51
A40
3152
5
6
7
8
9
A51
A51
10
3153
5060
Ground
Ground
Battery
Lane Departure Warning Indicator
Control
Ground
n.c.
GMLAN_1
GMLAN_2
LDW Switch GND (n.c., common
switch ground is used)
Lane Departure Warning Disable
Switch Signal
49
Pigtail Wire Color
Pigtail Wire Gauge
Terminal Plating
Shield Group
Circuit Description
Twist Group & Rate
Minimum Wire
Gauge
Max. Wire
Resistance
Circuit #
Cavity
1