The speed signal is generated by the vehicle 
speed sensor (at the transmission), and 
processed at the speedometer/odometer in the 
instrument cluster. 
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Continuation  
      If no speed was indicated:  
    
Notes: 
If the LED does not blink:  
 Electrical Wiring Diagrams, Troubleshooting & Component Locations   
If the wiring is OK and the LED does not blink:  
 Repair Manual, Electrical Equipment, Repair Group 90
    -  Connect VAG 1598/22 test box to ECM harness connector   Page 01
-
56
 . 
-  Connect VAG 1527B LED voltage tester between ECM/test box 
sockets 3 (B+) and 20 (signal). 
-  Lift vehicle at left front until wheel is free.
-  Switch ignition on and rotate left-front wheel by hand.
   LED must blink (very brief blink)
The right-front wheel must not rotate; block it if necessary.For LEDs with little voltage consumption, the LED lights up at half 
strength when the ignition is switched on. 
-  Check wiring from ECM connector, terminal 20 to instrument cluster for 
open circuit or short circuit 
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