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Procedure after voltage supply open circuit > < Wiring and component check with test box V.A.G 1598/22

A3 Mk1

Motronic injection and ignition system (4-cyl.)
Engine control unit
Checking control unit voltage supply

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

  • ◆ Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/3
  • ◆ Test box V.A.G 1598/22
  • ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
  • ◆ Adapter set V.A.G 1594
  • ◆ Current flow diagram

Check conditions

  • ● The fuses must be OK.
  • ● Earth connection between engine (on gearbox bell housing) and body (below battery) OK.
  • ● The battery voltage must be at least 11.5 V.
  • ● All electrical consumers, e.g. lights and rear window heating must be switched off.
  • ● If the vehicle is equipped with an air conditioning system, this must be switched off.
  • ● Alternator OK, checking:

=> Current flow diagrams, Electrical fault finding and Fitting locations

Test sequence

  • ‒ Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
    (Connecting fault reader and selecting engine control unit .)
 
→ Indicated on display:
Rapid data transfer    HELP
Select function XXX
  • ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.
 
→ Indicated on display:
Read measured value block
Input display group number XXX
  • ‒ Press keys 0, 0 and 4 for "Display group number 4" and confirm entry with Q key.
 
→ Indicated on display:
(1...4 = Display zones)
Read measured value block 4    ⇒
    1    2    3    4
  • ‒ Read off figure displayed in display zone 2.
        Specification: At least 11.5 V
  • ‒ Press the ⇒key.
  • ‒ Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
  • ‒ Switch off ignition.
 
N24-0709

If the specification is not attained:

  • ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness
    => Page 24-121.

Checking voltage supply terminal 30

  • ‒ Measure voltage supply with multimeter and aux. cables from V.A.G 1594 between test box sockets 2+15 and 15+28:
        Specification: min. 11.5 V

If the specification is not attained:

  • ‒ Check wiring connections to relay plate according to current flow diagram.

=> Current flow diagrams, Electrical fault finding and Fitting locations

Checking voltage supply terminal 15

  • ‒ Measure voltage supply with multimeter and aux. cables from V.A.G 1594 between test box sockets 2+27 and 27+28:
  • ‒ Switch on ignition.
        Specification: min. 11.5 V

If the specification is not attained:

  • ‒ Check wiring connections to relay plate according to current flow diagram.

=> Current flow diagrams, Electrical fault finding and Fitting locations

Procedure after voltage supply open circuit > < Wiring and component check with test box V.A.G 1598/22