Porsche training p95 advanced electrical systems

AfterSales Training
Advanced Electrical Systems
P95


Porsche AfterSales Training
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Training Center Location: ________________________________________________
Instructor Name: ________________________________________________
Date: ___________________

Electrical Troubleshooting Logic
1 - Do you understand how the electrical consumer is expected to operate?
2 - Do you have the correct wiring diagram?
3 - If the circuit contains a fuse, is the fuse okay & of the correct amperage?
4 - Is there power provided to the circuit? Is the power source the correct voltage?
5 - Is the ground(s) for the circuit connected? Is the connection tight & free of resistance?
6 - Is the circuit being correctly activated by a switch, relay, sensor, microswitch, etc.?
7 - Are all electrical plugs connected securely with no tension, corrosion, or loose wires?

Important Notice: Some of the contents of this AfterSales Training brochure was originally written by Porsche AG for its rest-ofworld English speaking market. The electronic text and graphic files were then imported by Porsche Cars N.A, Inc. and edited for
content. Some equipment and technical data listed in this publication may not be applicable for our market. Specifications are subject
to change without notice.
We have attempted to render the text within this publication to American English as best as we could. We reserve the right to
make changes without notice.
© 2015 Porsche Cars North America, Inc. All Rights Reserved. Reproduction or translation in whole or in part is not permitted
without written authorization from publisher. AfterSales Training Publications
Dr. Ing. h.c. F. Porsche AG is the owner of numerous trademarks, both registered and unregistered, including without limitation
the Porsche Crest®, Porsche®, Boxster®, Carrera®, Cayenne®, Cayman®, Macan®, Panamera®, Speedster®, Spyder®,
918 Spyder®, Tiptronic®, VarioCam®, PCM®, PDK®, 911®, RS®, 4S®, FOUR, UNCOMPROMISED®, and the model numbers and the distinctive shapes of the Porsche automobiles such as, the federally registered 911 and Boxster automobiles.
The third party trademarks contained herein are the properties of their respective owners. Porsche Cars North America, Inc.

believes the specifications to be correct at the time of printing. Specifications, performance standards, standard equipment,
options, and other elements shown are subject to change without notice. Some options may be unavailable when a car is built.
Some vehicles may be shown with non-U.S. equipment. The information contained herein is for internal authorized Porsche
dealer use only and cannot be copied or distributed. Porsche recommends seat belt usage and observance of traffic laws at
all times.

Part Number - PNA P95 007

Edition 6/15


Table of Contents

Description

Page

Section 1 – Data Bus Systems
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Data Bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Controller Area Network (CAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Local Interconnect Network (LIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Gateway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Vehicle Network State Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Network Topology Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Network Properties Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Section 2 – Energy Management
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Gateway Control Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
The Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Battery Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Current Distributor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Panamera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Cayenne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
9x1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Energy Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Fuses and Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Boxster/Cayman (981) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
911 (991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Cayenne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Macan (95B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Panamera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
911 (991) Driver and Passenger Fuse Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Cayenne (92A) Driver and Passenger Fuse Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Panamera (970) Driver and Passenger Fuse Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
DC/DC Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Actual Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Drive Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Advanced Electrical Systems

Page i


Description

Page

Section 3 – Immobilizer 5, FAZIT, & Component Protection

Engine Immobilizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Vehicle Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Electronic Ignition Lock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Immobilizer Master (Front Electronics) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Engine Control Unit (DME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Rear Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Central Door Locking and Alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Keyless Entry Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
KESSY System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Front BCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Rear BCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Rear Spoiler (Panamera) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Door Control Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Page ii

Advanced Electrical Systems


Data Bus Systems

Subject

Page

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Data Bus Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Controller Area Network (CAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Local Interconnect Network (LIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Gateway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Vehicle Network State Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Network Topology Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Network Properties Worksheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Advanced Electrical Systems

Page 1.1


Data Bus Systems
The following two illustrations show the “central locking”
function using the data bus method.

Introduction
Data Bus Systems
In order to meet the increasing requirements placed on
vehicle electronics with regard to vehicle safety, comfort,
communication, fuel consumption, reduction of exhaust
gases and diagnostics, it is essential that the individual
control units in the vehicle interact intensively.
The conventional method of organizing this interaction
used a separate line for every signal. Given the everincreasing amount of information to be transferred, this
method has reached its limits and this is why data bus
systems are used in current vehicles. These data bus
systems allow networking of control units and allow large
amounts of information to be made available.
Figures 9_115_12 and 9_116_12 show the central
locking system with the conventional method. All the input
information required is provided by sensors connected to
the “central locking” control unit. And the control unit is

hard-wired directly to all actuators.

Figure 9_115_12

In order to incorporate new functions, i.e. opening and
closing the windows using the remote control, another line
is required for each function and for each drive link, i.e.
four additional lines in this example.

ƒ – Central locking function

One control unit is the central locking master, in which all
possible functions are stored. In our example, this control
unit communicates with the door control units and all other
control units required for the “central locking” function via
CAN Comfort. For communication, only the bus lines are
required on each control unit. One (LIN) or two (CAN) copper lines or two optical waveguides (MOST®) are installed,
depending on the data bus system. Only a software enhancement is required in order to incorporate new functions.
All the information in all the control units can theoretically
be accessed by linking all control units in the vehicle network. To lock the vehicle as soon as a certain speed is
reached, the central locking master must simply receive
the speed signal from PSM. Opening the doors in the
event of an accident simply requires the crash signal,
which the airbag control unit sends to the CAN and which
the DME can also use to switch off the engine after an
accident, for example.
Network Structures

Figure 9_116_12

Page 1.2

The control units can be connected to a data bus in different ways, depending on where they are used, the number
of control units, the amount of information to be transferred and the required level of interference immunity. In
the descriptions below, the data lines are shown as one
line for greater clarity. For the CAN data bus, one line is
required for the CAN-low channel and one line for the CANhigh channel.

Advanced Electrical Systems


Data Bus Systems
Advantages: Relatively simple setup; simple retrofitting
options: To extend the ring, a control unit can be added
between two existing control units.

Star Structure

Disadvantages: The entire network fails in the event of
an open circuit. If one control unit is faulty, the message
can be corrupted for the other control units and can then
become unusable (“Chinese Whispers” principle). The ring
structure is used on the MOST® (Optical data bus/optical
waveguide) in Porsche vehicles.
Linear Bus Structure
In the star structure, all data lines are connected together
in one star point. If a control unit sends a message to the
data bus, it is immediately available to all other control
units on this network.
Advantages: Simple setup; relatively reliable since if there

is an open circuit in a line, all remaining control units on
the star can still communicate with each other.
Disadvantage: The connection point can be the weak
point: If it fails completely, communication is no longer
possible in the entire network.
The star structure can also be part of another network
(mixed structures; a pure star structure is not yet used at
Porsche).
Ring Structure

In the linear bus structure, the control units are connected
to the central lines via relatively short connecting lines.
Advantage: If one control unit fails, the others can still
communicate with each other.
Disadvantage: If there is an open circuit in the central
line at a connection point (splice point), several control
units fail.
The linear bus structure is primarily used in current
Porsche vehicles.

With a ring structure, one receive line and one transmit line
are connected to each control unit. Each control unit reads
the message and passes it on. Communication takes
place in one direction.

Advanced Electrical Systems

Page 1.3

Data Bus Systems
Controller Area Network – CAN

The data is transferred as follows:

Components
The CAN consists of one controller, one transceiver, two
data bus terminators (resistors) and two data bus lines
(CAN high/CAN low). With the exception of the data bus
lines, the components are located in the control units. On
the control units, the function of the components
has not changed.
They perform the following tasks:
The CAN controller receives the data to be transmitted
from the microcomputer in the control unit. It processes
the data and then forwards it to the CAN transceiver.
In the same manner, it receives the data from the CAN
transceiver, processes it and then forwards it to the microcomputer in the control unit.
The CAN transceiver is a transmitter and a receiver. It
converts the data from the CAN controller into electrical
signals and then transmits them to the data bus lines. In
the same manner, it receives data and then converts the
data for the CAN controller.
The data bus terminator is a resistor. It prevents transmitted data from being reflected back from the ends as an
“echo”, thereby corrupting the data. The data bus lines are
bidirectional and are used to transmit data. They are
designated as CAN high and CAN low.

The data to be transmitted is loaded into the CAN
controller by the control unit for transmission (Load data).

The CAN transceiver receives the data from the CAN
controller, converts it into electrical signals and then
transmits it (Transmit data).
All the other control units that are networked with the CAN
bus then become receivers (Receive data). The control
units check whether or not they need the received data for
their functions (Check data). If the data is important, it is
accepted and processed (Accept data), otherwise it is
ignored.

The data is transferred in digital form to the CAN, i.e. the
message is made up of a multitude of bits strung
together. The number of bits in a data frame depends on
the size of the data field.

This shows the systematic structure of a data frame. It is
identical on both data bus lines.
A – Terminating resistors

Note!
Data Transfer
With the CAN, no receiver is specified. The data is transmitted on the data bus and is generally received and
evaluated by all the users. This principle is also called
“Broadcasting”.

Page 1.4

One bit is the smallest unit of information (one switching
state per time unit). In electronic circuits, this information
can only ever have the value “0” or “1”, or “yes” or “no”.

Advanced Electrical Systems


Data Bus Systems
The start field is the start of frame and marks the start
of the data frame. A bit with approx. 3.5 V (depending on
the system) is sent on the CAN-high line and a bit with
approx. 1.5 V is sent on the CAN-low line (“Dominant bit”,
“0”).
The status field defines the priority of the data frame. If,
for example, two control units want to transmit their data
frame at the same time, the one with the higher priority is
given precedence.
The control field contains the number of information
units contained in a data field. This enables every receiver
to check that it has received all the information.
The data field transmits the actual information for the
other control units.
The CRC (cyclic redundancy check) field is used for
detecting transmission faults.
The acknowledge field enables a receiver to notify a
transmitter that it has received the data frame correctly. If
a fault is detected, it notifies the transmitter immediately.
Following this, the transmitter then repeats its transmission.
The end field ends the data frame as the end of frame.
This is the final opportunity to report faults that lead to
repetition of the transmission.

High-speed and Low-speed CAN

While previously, “slow” CAN systems with a data transfer
rate of 100,000 bits per second (100 kbits/s) and fast
CAN systems with a data transfer rate of 500,000 bits per
second (500 kbits/s) were still used at Porsche, only socalled high-speed CAN systems with 500 kbits/s are
installed in the Panamera, in the Cayenne E2 and in the
911 Carrera (991).
High-speed and low-speed CAN systems not only have
different data transfer rates, but also have different
voltage levels, which define dominant bits “0” and
recessive bits “1”. The number and size of terminating
resistors and the ability to continue to communicate when
a line fails are also different.
On the high-speed CAN, the difference between the signal
on CAN high and the signal on CAN low is always
evaluated.
On the low-speed CAN, if a line fails, the signal can
generally be evaluated on the line to ground that is still
functioning. Low-speed CAN systems are “single-wirecapable”.
Essentially, the same message is always transmitted on
CAN high and CAN low, but the voltages on both lines are
different. If the voltage on CAN high increases, it normally
falls by the same value on CAN low and vice versa.

Notes:

Advanced Electrical Systems

Page 1.5

Data Bus Systems
Interference Immunity

The voltage levels of a 500 kbits/s (high-speed) CAN bus are
shown above.

Note!
The duration of a bit on the high-speed CAN bus is:
1 second
500,000 bits
= 0.000002 seconds = 0.002 ms
Recessive bits (“1”) are transmitted with approx. 2.5 V on
the CAN-high line and on the CAN-low line.

In motor vehicles, it is important that the systems do not
have a negative, uncontrolled influence on each other.
Every current-carrying line creates a magnetic field. This
means that even in a data bus line, a change occurs in the
magnetic field around the data line whenever the voltage
changes (e.g. from bit “1” to bit “0”).
On the other hand, a change in the magnetic field in a line
also induces a voltage. The voltage depends on the
strength of the magnetic field, the position of the line with
respect to the field lines and the frequency of the change
in the magnetic field.
A system that interferes with another system is called a
“source of interference”. This system that is interfered
with is referred to as the “victim”. To prevent any interference acting on the data transmission, the two data bus
lines are twisted together.

If a dominant bit (“0”) is to be transmitted, the voltage on
the CAN-high line increases by approx. 1 V to approx. 3.5
V. At the same time, the voltage level on the CAN-low line
drops by approx. 1 V to approx. 1.5 V.

The voltage levels of a 100 kbits/s (low-speed) CAN bus are
shown above.

Note!
The duration of a bit on the low-speed CAN bus is:

A magnetic field in which the CAN bus line is located
therefore induces the same “interference voltage” in both
lines (“A” above). Since the control units evaluate the
difference between CAN high and CAN low, it is possible to
differentiate clearly between a dominant bit “0” and a
recessive bit “1”.

1 second
100,000 bits
= 0.00001 seconds = 0.01 ms
Recessive bits (“1”) are transmitted with approx. 0.2 V on
the CAN-high line and approx. 4.8 V on the CAN-low line. If
a dominant bit (“0”) is to be transmitted, the voltage on the
CAN-high line increases to approx. 3.75 V. At the same
time, the voltage level on the CAN-low line drops to
approx. 1.25 V.

Page 1.6

Advanced Electrical Systems


Data Bus Systems

At the same time, twisting also prevents interference
emission from the data bus line. The voltages are opposed
on the two lines during normal operation. In other words, if
the voltage on one data bus line increases by 1 V, then the
voltage on the other line drops by 1 V, and vice versa.
This ensures that total voltage is kept constant at all times
and the electromagnetic field effects of both data bus
lines cancel each other out. The data bus line is protected
against interference and is virtually neutral externally.

Bit-wise arbitration (data bus utilization control) for the multimaster concept is explained in greater detail using the above
example.

The front-end electronics (FEE), rear-end electronics (REE)
and a door control unit (door CU) start sending their data
frame at the same time. They also compare bit-for-bit on
the data bus line.

Multimaster Concept
If a control unit sends out a low order bit, but detects a
high order bit, it stops transmitting and starts receiving.
1st bit (red)

2nd bit

FEE sends a dominant bit

FEE sends a recessive bit

REE sends a dominant bit

REE sends a recessive bit

Door CU sends a dominant bit Door CU sends a recessive bit

3rd bit (blue)
FEE sends a dominant bit
REE sends a dominant bit
Door CU sends a recessive bit and detects a high-order bit on
the data bus line. It thus loses arbitration and becomes a
receiver.

Each control unit can send signals on the CAN. Since there
is no higher-order control unit or CAN master and because
only one message can ever be transmitted on the bus, a
multimaster concept is used for the CAN. In other words,
when several control units are attempting to send messages at the same time, the control unit that wants to
send the most important message is currently the master
and is thus authorized to send messages.

4th – 8th bit
FEE and REE both send the same bits, their message is currently
on the CAN bus.

9th bit (green)

FEE sends a recessive bit and detects a dominant bit on the data
bus line. It therefore loses arbitration and becomes a receiver.
REE sends a dominant bit and thus wins arbitration. It continues
to send its data frame up to the end.

The importance of the message is determined based on
its priority, which is indicated in the status field of the
message. The lower the binary numerical value in the
status field, the higher the priority of the message.

Once the REE has finished sending its data frame, the
others make another attempt to send their data frame.

Advanced Electrical Systems

Page 1.7


Data Bus Systems
Local Interconnect Network – LIN

LIN Master

The Local Interconnect Network (LIN) is primarily used to
transport data between control units and active sensors
and actuators. If there is a limited amount of data, it can
also be used for communication between control units. LIN
works according to the master/slave principle and only
uses one line. Address-oriented data transfer is another
feature that differentiates it from the CAN. In other words,

unlike broadcasting on the CAN, the transmitter’s messages for a defined receiver are specified. The data
transfer rate is 19.2 kbit/s.

The system facilitates data exchange between a LIN master
control unit and up to 16 LIN slave control units.

The LIN master has the following tasks:
• It controls the transfer of data and the data transmission speed and thus establishes the cycle for when
and how often each message will be sent on the LIN
data bus
• It sends out the message header
• It performs the translation function and acts as a gateway
The LIN master is the only control unit connected to the
CAN data bus in the LIN data bus system and therefore
allows diagnosis of the LIN slave control units using the
LIN master control unit.

Note!
The duration of a bit on the LIN is:
1 second
19,200 bits
= 0.000052 seconds = 0.052 ms

Notes:

Page 1.8

Advanced Electrical Systems

Data Bus Systems
LIN Slave

Transmission Reliability

Individual control units, or also sensors and actuators, can
be deployed as LIN slave control units within a LIN data
bus system. Electronics that evaluate the measured values
are integrated into the sensors. The values are then transferred as a digital signal via LIN. Only one pin is required
at the LIN master’s socket for multiple sensors and
actuators.

Data transfer stability is ensured by the specification of
tolerances during transmission and reception in the
recessive and dominant level range.

The LIN actuators are intelligent electronic or electromechanical assemblies that receive their tasks from the
LIN master control unit via the LIN data signal. The LIN
master uses the integrated sensors to query the actual
status of the actuators so that a required/actual comparison can be performed.
LIN Messages
Data Transfer
The sensors and actuators only respond if a header has
been sent out by the LIN master control unit.
Signal

Recessive level (“1”)
If no message or a recessive bit is sent via the LIN data
bus, the voltage on the data bus line is approximately
battery voltage.

Dominant level (“0”)
To transfer a dominant bit on the LIN data bus, the data
bus line in the sender control unit is switched through to
ground by a transceiver.

Advanced Electrical Systems

Page 1.9


Data Bus Systems
Message Header: Header
The header is sent by the LIN master control unit on a
cyclical basis.

The last 2 bits contain the checksum of the first 6 bits.
The checksum is used to detect transfer errors and is
necessary to avoid allocation to the wrong message in the
event of transfer errors in the identifier.

It can be divided into four sections:
•
•
•
•

The identifier field is 8 bit times in length. The first 6
bits contain the message ID and the number of data fields
in the response. The number of data fields in the response
can range from 0 to 8.

Sync break
Sync delimiter
Sync field
Identifier field

Message Header: Response
The response consists of 1 to 8 data fields. One data field
consists of 10 bits. Each data field comprises a dominant
start bit, a data byte (which contains the information) and
a recessive stop bit. The start and stop bits are used for
synchronization and to avoid transfer errors.

The sync break is at least 13 bit times in length. It is
sent at a dominant level. A length of 13 bits is required in
order to communicate the start of a message to all LIN
slave control units. A maximum of 9 dominant bits are
transferred consecutively in the subsequent message
parts.
The sync delimiter is at least 1 bit long and recessive
(≈ UBat).
The sync field consists of the bit sequence 0101010101.
All LIN slave control units can adjust to (synchronize with)
the system clock rate of the LIN master control unit via
this bit sequence. All control units must be synchronised
to ensure a fault-free exchange of data. If the synchronization is lost, the bit values would be positioned incorrectly
in the message when the receiver gets the message. This
would lead to errors in the data transfer.

Page 1.10

Advanced Electrical Systems


Data Bus Systems
Gateway
Several different data bus systems are installed in the
Porsche models.
Reasons for this include:
• Higher interference immunity: If one data bus system
fails, the other bus systems can still function.
• Different requirements placed on the data bus systems
with regard to data transfer rates, emergency operation
properties and physical properties.
• Operating reliability is only guaranteed when there is a
limited amount of data on a data bus system.
To enable the different data bus systems in the vehicle
network to connect with each other, gateway control units
(protocol converters) are installed.

This guarantees that data and information are exchanged
in spite of different transmission speeds, different transmission media, different levels of urgency of the information, different protocols and different signal levels of the
individual bus systems. Access to the individual control
units for diagnostic purposes is also possible centrally via
the gateway.
Wake-up Guardian
The Vehicle Network State Manager in the gateway control
unit defines the rules according to which communication
on a CAN bus begins (Wake-up) and ends (Sleep). Sleep
and wake-up problems on a bus can result in an increased

closed-circuit current.
The following rules apply for the Sleep and Wake-up
mode:

A gateway is a type of “interface”. The gateway gathers
information from various networks and sends information
to the correct network. The data that is sent out by the
various networks therefore goes into the gateway. The
speed, amount of data and levels of urgency of the individual messages are filtered here and “buffered” if
necessary.

• All control units on the bus are “awake” together.
• All control units on the bus “sleep” together.

The gateway converts the messages for the relevant
network based on gateway rules and conversion tables.
The messages are then sent to the relevant network and
reach their target address. Messages that are not that
important remain in the gateway’s memory, if necessary,
and are sent “later”.

The Wake-up guardian function is implemented in the
gateway control unit in order to identify activity that prevents sleep mode and activity that wakes the bus up in the
event of closed-circuit current problems. The wake-up
guardian can be activated and deactivated using PIWIS
Diagnostic Tester II and allows “on-board” data bus monitoring by recording network activities.

This means that a control unit that is not ready for sleep
mode keeps all the other control units “awake” or a control
unit wakes the other control units with “unnecessary” bus

activity. This results in a high closed-circuit current load.

Notes:

Advanced Electrical Systems

Page 1.11


Data Bus Systems
Vehicle Network State Manager

The Vehicle Network State Manager in the gateway ensures orderly wake-up and sleep initiation. Bus idle mode should be activated
on the networks 10 seconds after locking. To avoid loading the battery, bus idle mode is activated when terminal 15 is off. For
example, when the door handle is actuated, the door control unit sends a bus message to CAN comfort and wakes it up. If no
further activity is decteted on the CAN after 10 seconds, the Vehicle Network State Manager in the gateway issues the command
for the bus idle to CAN comfort.

Wake-up function
After terminal 15 is switched “off”, the gateway control unit sends the command Force sleep to all bus nodes in order to instruct all
bus nodes to switch to sleep mode. All control units send out their sleep readiness. To ensure that the individual bus systems are
then switched to sleep mode sequentially rather than in an uncontrolled manner, the Network Vehicle State Manager in the gateway
controls and monitors the individual network transition points in bus idle mode. To do this, the gateway sends out its sleep readiness to the individual networks. The same applies in reverse for waking. When a network is woken up by a connected control unit,
the gateway wakes up the other networks in this state. The networks then enter sleep mode again as described above.

Page 1.12

Advanced Electrical Systems

Data Bus Systems
Boxster (981) Network Topology

Diagnostics
500 kbps

Boxster (981) Network
twork T
Topology
opology
p gyy

PIWIS
IWIS T
Tester
ester II

DME

PDK

Selector Lever

PSM

Multiple Sensor

PASM
P
ASM / PADM

PADM

Driver Seat

Passenger Seat

Steering Column

POSIP

Seat Occupancy

Drive
500 kbps

Electronic
Electr
onic Parking Brake

Electric Power Steering

Chassis
500 kbps

Multifunction Steering Wheel

Comfort
Comfort
500 kbps

BCM Fr
Front
ont

Wiper
W
iper

Light Switch

Rain / Light Sensor
Ignition Switch

Gateway

Driver Door

BCM Rear

Steering Column Adjustment

Passenger Door

Overhead Console

Interior Surveillance

EC Mirr
Mirror
or

Alarm Sir
Siren
en

MOST
20 Mbps

MOST
PDLS/AFS Left

CDR 31

PDLS/AFS Right

Crash Risks
500 kbps

Man Machine
Interface
Inter
face
500 kbps
LIN
19.8 kbps

HomeLink

BOSE Amplifier

PCM 3.1
Instrument Cluster

Battery Sensor

Spor
ono
Sportt Chr
Chrono

Power Distributor

ParkAssist

Generator

TPM

DC / DC Conver
Converter

Operating and Air
Conditioning Unit

Air Quality Sensor
Heater Unit
Switch Module

Notes:

Advanced Electrical Systems

Page 1.13


Data Bus Systems
Cayman (981) Network Topology

Diagnostics
500 kbps

PIWIS Tester II

DME

PDK

Selector lever

Airbag

Seat occupancy

PSM

Multiple sensor

El. parking brake

PASM/PADM

El. power steering

Driver’s seat

Passenger’s seat

Combined steering column module

FEE/BCM-f

Wiper

Light switch

Drive
500 kbps
Chassis
500 kbps
Multi-function steering wheel

Comfort
500 kbps
Rain/light sensor

Gateway

ELV

Passenger’s door

Driver’s door

REE/BCM-r

Overhead operating
console/INC

EVLS
Interior
surveillance

EC mirror

VTS

MOST

MOST
20 Mbps
PDLS/AFS, left

PDLS/AFS, right

ACC

Crash risks
500 kbps
Man Machine
Interface

500 kbps

CDR 31
Instrument cluster

Battery sensor

Sport Chrono

Power distributor

ParkAssist

Generator

TPM

DC/DC

LIN
19.8 kbps

Notes:

Page 1.14

Advanced Electrical Systems

PCM 3.1
Operating &

A/C unit


Data Bus Systems
911 (991) Network Topology

Diagnostics
500 kbps

911 (991)
(
) Net
Network
twork Topology
Topology
p gyy

PIWIS
IWIS T
Tester
ester II
DME

PDK

Selector Lever

POSIP

Seat Occupancy

Drive
500 kbps

PSM

Multiple Sensor

PASM
P
ASM / PADM
PADM

Electronic
Electr
onic Parking Brake

PDCC

Electric Power Steering

Chassis
500 kbps

Driver Seat

Passenger Seat

BCM Fr
Front

ont

Front
Fr
ont W
Wiper
iper

Cabriolet
let Top
Top

Steering Column

Multifunction Steering Wheel

Comfort
Comfort
500 kbps

Light Switch

Rain / Light / Humidity Sensor

Ignition Switch

Steering Column Adjustment

Gateway
BCM Rear

Driver Door

Overhead Console

Interior Surveillance

Driver Door Rear (Cabriolet)

EC Mirr
Mirror
or

Passenger Door

Alarm Sir
Siren
en

Passenger Door Rear (Cabriolet)

MOST
20 Mbps

MOST
PDLS/AFS Left

CDR 31

PDLS/AFS Right

Crash Risks
500 kbps

Man Machine
Interface
Inter
face
500 kbps

HomeLink

PCM 3.1
Instrument Cluster

Battery Sensor

Spor
ono
Sportt Chr
Chrono

Power Distributor

ParkAssist

Generator

TPM

DC / DC Conver
Converter

LIN
19.8 kbps

Operating and Air
Conditioning Unit

BOSE Amplifier
Burmester Amplifier

Air Quality Sensor
Heater Unit
Switch Module

Notes:

Advanced Electrical Systems

Page 1.15


Data Bus Systems
Cayenne (92A) Network Topology

Diagnostics
500 kbps

Cayenne

Ca
ayenne
y
(92A)
(
) Network
twork Topology
Topology
p gyy

PIWIS
IWIS Tester
Tester II
DME

Tiptronic
Tiptr
onic

Selector Lever

POSIP

Seat Occupancy

Drive
500 kbps

PSM

Multiple Sensor

Differential
Dif
ferential Lock

Electronic
Electr
onic Parking Brake

All Wheel Hang On

PDCC

PASM
P
ASM / Level Control
Control

Chassis
500 kbps

Driver Seat

Passenger Seat

Trailer
T
railer Hitch

Front
Fr
ont Wiper
Wiper

Light Switch

Power Lift Gate

Steering Column

Multifunction Steering Wheel

Comfort
Comfort
500 kbps

BCM Fr
Front
ont

Rain / Light / Humidity Sensor

Steering Column Adjustment

Gateway
BCM Rear

MOST
20 Mbps

Driver Door

Overhead Console

Sliding Roof

Driver Door Rear

EC Mirror
or

Passenger Door

Steering Column Lock
(Up to MY 11)

Ignition Switch

HomeLink

Panorama Roof

Passenger Door Rear

MOST
CDR 31

PDLS/AFS Left

PDLS/AFS Right

Control
Adaptive Cruise Contr
ol

Blind Spot Detection

Crash Risks
500 kbps
Man Machine
Interface
Inter
face
500 kbps

LIN
19.8 kbps

PCM 3.1
Instrument Cluster

Compass

ParkAssist

TPM

Power Distributor

Generator

DC / DC Conver
Converter
ter

Notes:

Page 1.16

Fr
ont Operating and
Front
Air Conditioning Unit

Advanced Electrical Systems

BOSE Amplifier
Burmester Amplifier

Heater Unit
Air Quality Sensor

Chassis Contr
Control
ol Switch
Battery Sensor

Alarm Sir
Siren

en

Sun Sensor
Rear Operating and
Air Conditioning Unit


Data Bus Systems
Macan (95B) Network Topology

Notes:

Advanced Electrical Systems

Page 1.17


Data Bus Systems
Panamera (970) Network Topology up to MY13

Diagnostics
500 kbps

Panamera (970) Network
twork T
Topology
opology
p gyy

PIWIS

WIS T
Tester
ester II
DME

Generator

PDK

Selector Lever

POSIP

Seat Occupancy

Drive
500 kbps

PSM

Multiple Sensor

Differential
Dif
ferential Lock

Electronic
Electr
onic Parking Brake

PDCC

PASM
P
ASM / Level Control
Control

Chassis
500 kbps

Driver Seat

Power Lift Gate

Passenger Seat

Steering Column

Multifunction Steering Wheel

Comfort
Comfort
500 kbps

BCM Fr
Front
ont

Gateway
BCM Rear

MOST
20 Mbps

Driver Door

Front
Fr
ont Wiper
Wiper

Light Switch

Rain / Light / Humidity Sensor

Tire
Tir
e Pr
Pressure
essure Monitoring

Reversing Camera

Overhead Console

Sliding Roof

Driver Door Rear

Steering Column Adjustment

EC Mirr
Mirror
or

Passenger Door

Steering Column Lock
(Up to MY 11)

Ignition Switch

HomeLink

Alarm Sir
Siren
en

Passenger Door Rear

MOST
PDLS/AFS Left

PDLS/AFS Right

Adaptive Cruise Contr
ol
Control

Blind Spot Detection

Crash Risks
500 kbps

Instrument Cluster

Sport Chrono
Chrono
Sport

CDR 31
PCM 3.1

ParkAssist

Man Machine
Interface
Interface
500 kbps

Front
Front Operating and
Air Conditioning Unit

BOSE Amplifier
Burmester Amplifier

Heater Unit
Air Quality Sensor

Battery Sensor

LIN
19.8 kbps

Power Distributor
Rear Operating and Air Conditioning Unit

Notes:

Page 1.18

Advanced Electrical Systems

Pressure
Pr
essure Sensor


Data Bus Systems
Panamera (970) Network Topology from MY14

Notes:

Advanced Electrical Systems

Page 1.19


Data Bus Systems
Sports Cars (9x1) Network Properties

Notes:

Page 1.20

Advanced Electrical Systems


Data Bus Systems
Cayenne E2 (92A) Network Properties

Notes:

Advanced Electrical Systems

Page 1.21