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 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

• ‒ Note intake air temperature figure in display zone 2.

     1)     If a temperature is displayed which deviates greatly from the ambient temperature of the sender, check sender wiring for transfer resistances.

     2)     Check is only possible when the engine is cold.

Continuation of check when display -40 °C:

• ‒ → Pull 2 pin connector -1- of coolant temperature sender (G62) -2-.
• ‒ Bridge connector contacts with aux. cables from V.A.G 1594 and observe display.

Display 120 ° C:

• ‒ Replace coolant temperature sender -2-.

Display -40 ° C:

• ‒ Press ⇒ button.
• ‒ 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 wire between test box socket 14+2 pin connector contact 1 for open circuit according to current flow diagram.
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wire for short to battery positive.
       Specification: ∞ω

If no fault in wire is detected:

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

Continuation of check when display = 120 °C:

• ‒ → Pull 2 pin connector -1- off coolant temperature sender (G62) -2-.

Display -40 ° C:

• ‒ Replace coolant temperature sender -2-.

Display 120 ° C:

• ‒ Press ⇒ button.
• ‒ Input 06 for "End output" and confirm with Q.
• ‒ Switch off ignition
• ‒ Pull connector off Digifant control unit.
• ‒ Check wire between control unit connector and 2 pin connector contact 1 for short to wire contact 2 and to vehicle earth, according to current flow diagram.
       Specification: ∞ω

If no fault in wire is detected:

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

Continuation of check when display = coolant temperature:

Functional check of sender

• ‒ Observe coolant temperature figure in display zone 2. The temperature figure must
       Increase uniformly and without interruption.

Notes:

• ◆ Depending upon the temperature level, the display on fault reader will jump by 2...5 °C
• ◆ If irregular engine running occurs in certain temperature ranges and the temperature figure does not increase without interruption, the temperature signal is temporarily interrupted and the sender must be renewed.

• ‒ Press ⇒ key.
• ‒ In put 06 for "End output" and confirm with Q.