Volkswagen Workshop Service and Repair Manuals

Checking function

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 engine idling.
  

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

• ‒ Input 01 for "Display group number" and confirm with Q.

Note:

If something different is indicated on the display:

=> Fault reader operating instructions

• ‒ Observe 4th position from left in display zone 4 -8 digit number block-.
       Specification: 0
• ‒ Open throttle valve slightly. The display at position 4 must jump to 1
       Display: 00010100

If the specifications are not attained:

Continuation of check when display = always 0:

• ‒ → Pull 2 pin connector -1- off idling switch (F60) -2-.

Display 1:

• ‒ Replace idling switch -2.

Display 0:

• ‒ Press ⇒ key.
• ‒ Input 06 for "End output" and confirm with Q.
• ‒ Switch off ignition
• ‒ Pull connector off Digifant control unit.
• ‒ Check wiring to control unit at 2 pin connector contact 1 for short to wire contact 2 and to vehicle earth.

If no fault in wire is detected:

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

Continuation of check when display = always 1:

• ‒ → Pull 2 pin connector -1- off idling switch (F60) -2-.
• ‒ Bridge connector contacts with aux. cables from V.A.G 1594 and observe display.

Display 0:

• ‒ Replace idling switch -2.

Display 1:

• ‒ 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.
• ‒ Check wiring between test box and 2 pin connector for open circuit according to current flow diagram.
       Contact 1+socket 21
       Contact 2+socket 33
       Wire resistance: Max. 1.5 ω

If no wiring fault is detected:

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

Renewing idling switch

Special tools, testers and auxiliary items

• ◆ Vernier caliper or depth gauge

Work sequence

• ‒ Remove throttle valve housing.

• ‒ → Measure and note dimension throttle valve to sealing surface -a-.
• ‒ Renew idling switch (F60) -1-.
• ‒ Adjust throttle valve by moving the idling switch -1- so that the dimension -a- is set again.

Note:

Setting the throttle valve must be carried out very carefully. On no account must the dimension -a- be exceeded.

Adjusting idling switch

Special tools, testers and auxiliary items

• ◆ Vernier caliper or depth gauge

Work sequence

• ‒ → Loosen idling switch -1- .
• ‒ Slowly close throttle valve (the stop on the cam must not touch the idling switch).
• ‒ Measure and note distance from throttle valve to sealing surface -a-.
• ‒ Adjust throttle valve by moving the idling switch -1-.
       Adjusting dimension a = noted dimension a + 0.5 mm

Note:

The throttle valve adjustment must be carried out very carefully. On no account must the adjusting dimension -a- be exceeded.