Volkswagen Workshop Service and Repair Manuals

Special tools, testers and auxiliary items

• ◆ Fault reader V.A.G 1551 with cable V.A.G 1551/3
• ◆ Test box V.A.G 1598/18
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test sequence

• ‒ Connect fault reader V.A.G 1551 and select engine electronics control unit (address word 01); carry out selection with ignition switched on.
  

• ‒ Input 08 for "Read measured value block" function and confirm with Q.

• ‒ Enter 03 for "Display group number" and confirm with Q.

Note:

If something different is indicated on the display:

=> Fault reader operating instructions

• ‒ Read-off throttle valve angle in display zone 3.
       Specification: 0 <°
• ‒ Slowly open throttle valve and watch angle display in display zone 3.
  The figure must increase uniformly over
       the complete range.

Note:

The displayed figure is dependent on the tolerances of the throttle valve potentiometer and does not correspond to the actual opening angle. The maximum permissible displayed figure is 86 <°.

If the figure does not increase uniformly:

• ‒ Replace throttle valve potentiometer (G69).

If the display shows constant 0 <° or approx. 90 <°:

Continuation of check when display 0 <°:

• ‒ → Pull 3 pin connector -1- off throttle valve potentiometer -2-.
• ‒ Bridge contacts 1+2 of connector with aux. cables from V.A.G 1594 and observe display.

Display 90 <°:

• ‒ Replace throttle valve potentiometer -2-.

Display 0 <°:

• ‒ Check voltage between contacts 1+3 on plug.
       Specification: approx. 5 V
• ‒ Press ⇒ key.
• ‒ Input 06 for "End output" and confirm with Q.
• ‒ Switch off ignition

• ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.

If voltage of about 5 V was present:

• ‒ Check wire between test box socket 40+3 pin connector contact 2 for open circuit according to current flow diagram.
       Wire resistance: max. 1.5 ω
• ‒ Additionally check wire for short to earth.
       Specification: ∞ω

If no voltage was present:

• ‒ Check wire between test box socket 41+ 3 pin connector contact 1 also socket 33+contact 3 for open circuit according to current flow diagram.
       Wire resistance: max. 1.5 ω

If no wiring fault is detected:

• ‒ Renew Digifant control unit (J169)
  , item 11 .

Continuation of check when display = approx. 90 <°:

• ‒ → Pull 3 pin connector -1- off throttle valve potentiometer -2-.

Display 0 <°:

• ‒ Replace throttle valve potentiometer -2-.

Display 90 <°:

• ‒ Check voltage between contacts 1+2 on connector and note.
• ‒ Press ⇒ key.
• ‒ Input 06 for "End output" and confirm with Q.
• ‒ Switch off ignition
• ‒ Pull connector off Digifant control unit.

If voltage of about 5 V was present:

• ‒ Check wiring at 3 pin connector contacts 1+2 for short to one another according to current flow diagram.

If the voltage was approx. battery voltage:

• ‒ Check wire at 3 pin connector contact 2 for short to battery positive according to current flow diagram.

If no wiring fault is detected:

• ‒ Renew Digifant control unit (J169)
  , item 11 .