No communication with the electronic unit
Symptom: The seat can be operated by the manual controls but when the manual control is released the seat returns to its original position.
 
  
 
 
  
   
    
     |  | No communication with the electronic unit | 
   
  
  
  
  
   
  
  
  
   
    
     
      | 1. | that the ignition is switched on and the electronic unit is supplied with battery voltage. 
 
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      | 2. | that battery voltage is present across pins 16 and 4 of the test socket (if the voltage is correct, the ISAT display will light up when the ISAT is plugged into the test socket). 
 
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      | 3. | the connection between the test socket and the electronic unit. 
 
   
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      | 4. | If the ISAT still cannot establish communication with the electronic unit: 
 
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   Symptom 1
  
  
   The seat can be operated by the manual controls but when the manual control is released the seat returns to its original position.
   
   
   
    Probable cause of fault 1:
   
  
  
   
   
  
  
  
   
    
     
      | • | Fault in the memory button assembly. The memory buttons are constantly activated. 
 
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   Diagnostic procedure 1:
  
  
   Turn to page 852-52 "Checking the operation of pushbuttons and manual controls".
   
   
   
    Symptom 2
   
  
  
   The electronic unit is completely dead and does not react in any way to commands from either the memory pushbuttons or the manual controls.
   
   
   
    Probable cause of fault 2:
   
  
  
   The electronic unit has detected an internal fault of such a nature that all functions have been blocked.
   
   
   
    Diagnostic procedure 2:
   
  
  
   Turn to page 852-55, "Before control module replacement".