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01-2
       When the data link has been established, you 
can then select the required troubleshooting 
functions provided. The functions represent 
program sequences within On Board Diagnostic 
(OBD). Their application is described in the 
appropriate sections of this repair manual. After 
first checking the control module version, start 
the troubleshooting procedure with "Check DTC 
Memory" function 02.  
      Any DTCs which may be stored in DTC memory 
will be indicated on the display of the scan tool. 
Diagnostic information leads via DTC tables to 
possible causes and specific repair procedures. 
DTC tables are located in the appropriate 
sections of this repair manual.  
      The OBD distinguishes between "static" and 
"sporadic" malfunctions. If a malfunction which 
has been stored as "static" is no longer present 
when the ignition is switched on, it is converted 
to "sporadic".  
      Sporadically occurring malfunctions are indicated 
as such. "/SP" will appear at right on the tester 
display.  
      A sporadic malfunction is erased automatically if 
it no longer occurs after a certain number of 
driving cycles.  
Pa
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        Page 4 of 12
01-3
       Static malfunctions remain stored until DTC 
memory is erased using the Scan Tool (ST).  
      Check control module version before replacing 
control module. This appears in the display of the 
scan tool together with the coding when 
communication is established between the 
control module and the scan tool.  
Pa
ge 4 of 12 On Board Dia
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play?action=Goto&t
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        Page 7 of 12
01-6
 
VAG - On Board Dia
gnostic 
HELP
1 - Rapid data transfer1)2 - Blink code output1
)
    
Indicated on display:  1) Appear alternately on display  
Notes: 
 Electrical Wiring Diagrams, Troubleshooting & Component Locations   If nothing is indicated on display, check diagnostic connection.
    
The PRINT button is used for switching on the printer. Indicator lamp 
in the button comes on when printer is switched on. Depending on the program, additional operating information can be 
printed out by pressing the HELP button of the VAG1551 scan tool. 
Pa
ge 7 of 12 On Board Dia
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play?action=Goto&t
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        Page 8 of 12
01-7
      
-  Switch ignition on.
     
-  Switch printer on by pressing PRINT button on 
scan tool. 
     
-  Press button -1- to select "Rapid data transfer" 
operating mode 1. Rapid data transfer 
HELP
Insert address word XX
    
Indicated on display:  
Note:  
The address word selects the control module that you wish to test using 
the scan tool. The address word consists of two digits and is indcated in 
the relevant section of this repair manual. 
Pa
ge 8 of 12 On Board Dia
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play?action=Goto&t
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        Page 9 of 12

01-8
      
Note:  
     For example: Pressing buttons -0- and -3- 
selects the "Brake Electronics" address word 03. Rapid data transfer 
Q
03 Brake electronics
    
Indicated on display:  
Rapid data transferScan tool sends address word 03 -  Press -Q- button to confirm input.
    Indicated on display after entering address word 03:  
Note:  
If a malfunction occurs when establishing communication between the 
VAG1551 scan tool and the control module, refer to the four displays and 
instructions that follow. 
Rapid data transfer 
HELP
Control module not respondin
g!
     
Rapid data transfer 
HELP
K-wire not switchin
g to Ground / B+
    
-  Press the "HELP" button to print a list of possible causes of the 
malfunction. 
Rapid data transfer 
HELP
No si
gnal from control module
    
 Electrical Wiring Diagrams, Troubleshooting & Component Locations    -  Test cable connections for data link connector wire -K-.-  Test power supply and Ground (GND) connections for ABS control 
module (w/EDL) -J104-. 
Pa
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play?action=Goto&t
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        Page 11 of 12
01-9
 
Rapid data transfer 
HELP
Error in communication link
    
If displayed:  
 Electrical Wiring Diagrams, Troubleshooting & Component Locations    -  Repair the malfunction. -  After repairing the malfunction, once again enter "Brake Electronics" 
address word 03 and press -Q- button to confirm. 
Pa
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        Page 12 of 12

01-10
 
XXX XXX XXX 
YYY YYY YY YY YY 
ZZZ 
Codin
g VVVVV 
WSC WWWWW
    
If the data link between the scan tool and the control module is 
established and works properly, the display will now show the control 
module identification (X), the system identification (Y), the hardware and 
software versions (Z), and the dealership number (W).  
Notes: 
 Parts catalog   
 Electrical Wiring Diagrams, Troubleshooting & Component Locations   
The   button is used for advancing through the program sequence.The various On Board Diagnostic (OBD) systems to be tested are 
described in more detail in the relevant sections of this Repair Manual 
booklet. The control module index can only be changed by replacing the 
control module. If the control module identification number does not appear in the 
display, check the diagnostic wiring. 
- 
Press  button.
Rapid data transfer 
HELP
Select function XX
    
Indicated on display:  
Pa
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play?action=Goto&t
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e=re
pair&id=AUDI.B5.SU02.01.1