I/K Bus Topology

MRS III IHKA

0

EWS 3.3

RDW
80 60 40

60

100 120 140

220 240

3 2 1 0
40
!

4
1/min x 1000

120 140 100 160 180 80 200

5 6 7

40
20

20
km/h

HIGH INSTRUMENT CLUSTER

P
!
ABS

MPH

70 0 F

640 F
A
CHECK ENGINE
OIL SERVICE INSPECTION

ELECTRONIC

20 15

10

123456

miles

122 4

+72 0F

AUTO

REST

K-BUS

K-BUS

20

DIGIT

READOUT

PRND S 432

DIAGNOSIS BUS

M-BUS

SZM
Antenna Amplifier

LWR
1 2 3 FM

BMBT
INFO 4 5 6 AM
On-board computer DSP Code Emergency Monitor off

MENU
GPS-Navigation Aux. Ventilation

I-BUS

TONE SELECT

M M M M

FZV

GM III
P-BUS

DWA

MODE

Set

MENU

CAN BUS

11.13.2000 Thursday

10:17

MK 3 NAV
B

MFL

SRS AIRBAG
POWER

GPS NAVIGATION SYSTEM

Driver's Door Switchblock/ Module PM-FT/SB

CHECK ENGINE

Passenger's Door Module PM-BT Sunroof Module PM-SHD

RADIO LCM CMT 7000 interface box

DSP

LEW

Seat Memory Module PM-SM

DSC III
PDC

CDC
obd ii STANDARDIZED FAULT CODES
1

AGS DME

Sc
2

an
3

ne
4

Y N

OBD II CONNECTOR TXD II

BMW
BMW DIS

DIS

{
CHECK ENGINE

DIAGNOSIS BUS
20 PIN DIAGNOSTIC CONNECTOR up to 9/00 TXD

BMW DIS

Example: E39 High Version with I and K bus network.

KOMBI
DIAGNOSIS BUS (TXD)
80 60 40

60

RAIN SENSOR AIC

EW S3
MR S3

100 120 140

220 240

3 2 1 0
40
!

4
1/min x 1000

.3

120 140 100 160 180 80 200

5 6 7

40
20

20
km/h

MPH
ELECTRONIC

20 15

10

012345 km 1224

miles

PRND S321
OIL SERVICE INSPECTION

ABS

DSC III
!

HC SO B

K-BUS

K-BUS

CHECK ENGINE

MP MP

+ 88 8

L/100 KM/H KM/L

K-BUS

RADIO

CAN BUS

IHKA
70 0 F
AUTO

RECEIVER MODULE

- BASS + - TREBLE +

DOLBY SYSTEM

FLAT

FADER BALANCE

640 F

FBZV
A

P-BUS

IHKA

GM III

DWA
m
AUDIO TEL BC

0 0: WH
228 390 14 1 7 0 0:W 3W H MB

AUTO

REST

SRS AIRBAG

M-BUS

K-BUS
B
W

K-BUS MID
Telephone Interface Box

MFL-CM

DIAGNOSIS BUS

M-BUS

K-BUS

M M M M

Driver's Door Switchblock/ Module FBZV GM PM-FT/SB III

Psgr's Door Switchblock/ Module DWA PM-FT/SB Sunroof Module PM-SHD

DME
LCM III
AMPLIFIER
SRS AIRBAG

AGS

P-BUS

Seat Memory Module PM-SM Driver's Door

Switchblock/ Module PM-FT/SB Seat Memory Module PM-SM

Passenger's Door Module PM-BT Sunroof Module PM-SHD

OBD II - DLC

MID

BMW

RADIO

StarTAC

GR II

PDC

MFL-CM

AMPLIFIER

obd ii STANDARDIZED FAULT CODES

1 2 3

Sc

an

ne

LCM
TXD II

ABS/ASC5
EHC
CAN BUS

LWR

(diagnostic link connector)

DIS BMW
BMW DIS

obd ii STANDARDIZED FAULT CODES

1

Sc
2

an
3

er

{
20 PIN DIAGNOSTIC CONNECTOR

DIAGNOSIS BUS
TXD

AGS

18

Example: DME E53 Base Cluster with K bus network . DIAGNOSIS BUS
EWS II MRS

BMW DIS

Bus System Troubleshooting

oD

iC

The I/K bus consists of a single copper wire. The wire color of the I and K bus is uniform throughout the vehicle with: I-bus WS/GR/GE and the K-bus WS/RT/GE (Note: 2001 E39s with base Kombi have changed K-bus wire color to the same as the I-bus, WS/GR/GE). Due to the linear structure of the network, the I/K bus is available for other modules in the event of a disconnected or failed control unit. Just as the CAN bus, this is referred to as a Tree structure with each control unit occupying a branch. The I/K-bus provides the diagnostic connection to the control units located on those busses (except IKE/KOMBI).
Always refer to the ETM to determine the exact wiring configuration and color for a specific model.

Troubleshooting the I/K bus

The failure of communication on the I/K bus can be caused by several sources: Failure of the bus cable. Failure of one of the control units attached to the bus. Failure of the voltage supply to individual modules. Interference in the bus cables.

The I/K bus is active when KL R is switched on, it remains active until 60 seconds after the last message. If the key is switched off (KL30) the bus may be activated for a time by individual users via a wake-up message.
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Unlike the CAN bus where each control unit (subscriber) provides voltage for communication, the I/K-busses use only determined Master or Stand-by Controllers to supply B+for communication. The voltage level on the I/K bus must be above 7V. The nominal value should be close to the system voltage of the vehicle. Just like the CAN bus, the fact that voltage is present does not mean that the bus is fault free, it just means that the voltage level is sufficient to support communication.

BMW Test system Multimeter

Freeze image

10.15 V DC
Minimum Maximum 20 Measurement Function Voltage V Current 2A Measurement Connection Measurement Kind Resistance Ohm Current 50A 0 Temperature
o

20

System voltage Rotation speed

C Diode test Pressure bar

Current 1000A

-|>|Pressure Sensor

2nd measurement

MFK 1

MFK 2

Current probe

Temperature Sensor

=
automatic

Effective value

Measurement Range

500 mV

Stimulate

Multimeter

Counter

Oscilloscope setting

Stimulators

Preset measurements

Bus System Troubleshooting

19

Control units that provide operating voltage to the I/K bus are: On E38 and E39/E53 High version vehicles: The LCM is the Master Controller of the I-bus. The IKE and MID/BMBT are Stand-by Controllers. The GM is the Master Controller of the K-bus.

On E46, E52 and E39/E53 Base version vehicles: The GM is the Master Controller for vehicles equipped with only the K-bus. The LCM/LSZ is the Stand-by Controller.

Failure of the Bus cable The following faults can occur to the I/K bus wiring: Short Circuit to B+ Short Circuit to BBus line down (open) Defective plug connections (damaged, corroded, or improperly crimped)

Short Circuit to B+: Modules that send a message see that the message was not received and that the bus remains high. However, subscribers are unable to decide whether the fault is due to a shorted line or a defect in the communication interface. The module will repeat its message 5 times before discontinuing and faulting. The module will continue to operate as normal minus any commands that could not be delivered by the bus. Short Circuit to B-: The subscribers do not interpret a low bus line as a fault but just as a bus line deactivation. The Master and Standby controllers do detect the short and enter it as a bus fault. (No communication). Bus Line Down: The bus line may be open at any of several locations. As long as the Master or Stand-by is still connected, communication can occur with any modules still remaining. The fault situation will be the same as if the disconnected modules were defective themselves. Checking the bus line is carried out just like any other wiring. Perform continuity tests between the connections of different modules (all modules disconnected) without forgetting to make sure that the bus has not shorted to ground or another wire. It is recommended to use the Wire Test in Preset Measurements which is more sensitive than just a resistance check. 20

Bus System Troubleshooting

If Voltage level and the wire test are O.K then looking at the communication signal may be useful. In order to get a signal, operate different devices on the I/K bus (e.g. MID/MFL) to stimulate conversations. The following are some examples of scope patterns that may be observed when checking the I/K bus.
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BMW Measuring system Oscilloscope display

A [V]
Cursor 1 Memory Cursor 2 Freeze Image

8 [V]

V
Channel B

V High
7V to B+

16 12 8 4 0 -4 -8 -12 -16

16 12 8 4 0 -4 -8

8 6 4 2 0 -2 -4

T r i g g e r

Zoom

Amplitude Channel A

V Low
0V to 2V

Amplitude Channel B

l e v -12 -6 e -16 -8 l
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Time value

Message Time
5ms to 30ms
Stimulate

ms

Multimeter

Counter

Oscilloscope setting

Stimulators

Preset measurments

61400100

Example of correctly operating I/K bus during communication

Correct communication on the I/K bus occurs in sporadic bursts with periods of steady voltage around 12V.
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BMW Measuring system Oscilloscope display

A [V]
Cursor 1 Memory Cursor 2 Freeze Image

BMW Measuring system Oscilloscope display

8 [V] V
Channel B

A [V]

Cursor 1

Memory

Cursor 2

Freeze Image

8 [V]

V
Channel B

16 12 8 4 0 -4 -8 -12 -16

16 12 8 4 0 -4

8 6 4 2 0 -2

T r i g g e r

16
Zoom

16 12 8 4 0 -4

8 6 4 2 0 -2

12 8

Amplitude Channel A

4 0

T r i g g e r

Zoom

Amplitude Channel A

Amplitude Channel B

-4 -8

Amplitude Channel B

l -8 -4 e v -12 -6 e -16 -8 l
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Time value

-12 -16

l -8 -4 e v -12 -6 e -16 -8 l
-2.0 -1.0 -1.5 -0.5 0.0 0.5 1.0 1.5 2.0

Time value

ms

Stimulate

ms

Stimulate

Multimeter

Counter

Oscilloscope setting

Stimulators

Preset measurments

Multimeter

Counter

Oscilloscope setting

Stimulators

Preset measurments

61400100

Flat line at 12 volts No communication is currently taking place. The bus may be temporarily offline or shorted to B+.

Flat line at 5 volts No output voltage from the Master or Standby controllers. Bus line may be open or control unit may be defective.
Bus System Troubleshooting

61400100

21

Failure of one of the control units attached to the I/K bus. Each control unit connected to the bus has an integrated communication module that makes it possible for that control unit to exchange information. Failure of a control unit normally triggers a fault code in the other control units connected to the bus. As a quick check for the I/K-bus, activate the four way flashers. The flash indicators must light up in the instrument cluster. Switch on the Radio, and adjust volume using the MFL or MID/BMBT, the volume must change accordingly. On High version vehicles press the recirculation button on the MFL, The IHKA should respond to the request. This test checks the gateway link as well as the the I and K bus communication. If the tests prove O.K, this means that communication on the bus is O.K. Any faults still existing can only be related to faults specific to a control unit or a local I/K-bus wiring defect to a module. There are instances where failures may be software related. A faulted module may paralyze or take down the entire bus. This scenario would be evident by functions not being carried out and and possible faults stored. In order to isolate the defective control unit, the control units can be disconnected one at a time. Repeat the bus test after each disconnected control unit. If the disconnected control module is the defective one the faults will only point to communication with that interrupted module and no one else. Once the module has been replaced (observing current S.I.Bs) and coded, perform the I or K bus Test Module in the Diagnosis Program to ensure that communication is O.K. Failure of the voltage supply to individual modules. A slowly dropping battery voltage on a vehicle with discharged battery can lead to sporadic communication faults in various control units on the bus. The reason is that not all control units will switch off communication at the same voltage level leaving some modules still trying to communicate. Always verify a properly charged battery and charging system and fuses before beginning troubleshooting on the bus. Also, do not forget to check for a proper ground to a control unit, this may not allow the bus to see a signal low (0-2V) Interference in the bus cables. Interference will have a similar effect to shorting or disturbing the bus wiring. Excessive interference created by a defective alternator or aftermarket devices such as cell phones or amplifiers may induce a voltage into the bus line and disrupt communication. This type of interruption may be intermittent and faults may only be stored in some modules and not in others. These faults are often difficult to reproduce. Isolate any aftermarket wiring in the vehicle and see if the fault returns. 22
Bus System Troubleshooting