Volkswagen Workshop Service and Repair Manuals

Special tools, testers and auxiliary items

• ◆ 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 1598/18
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test conditions

• ● Engine cold

Test sequence

• ‒ Start engine and run at idling speed.
• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronic control unit (address word 01). Carry out selection at 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

Functional check of sender

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

If a temperature figure is displayed with deviates greatly from the senders ambient temperature, check sender wiring for transfer resistance.

Note:

• ◆ Depending upon the temperature level, the displayed 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
• ‒ Input 06 for "End output" and confirm with Q.

If the figure does not increase uniformly:

• ‒ Replace coolant temperature sender -2-.

If a -G62- fault is indicated in fault memory even though the figure increases uniformly:

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

• ‒ → Pull 4 pin connector -1- of coolant temperature sender (G62) -2-.

• ‒ → Check wiring between test box and 4 pin connector for open circuit according to current flow diagram.
       Contact 1 + socket 17
       Contact 3 + socket 42
       Wire resistance: max. 1.5 ω
• ‒ Check wiring between control unit connector and 4 pin connector contact 3 for short to wire contact 1 and to vehicle earth, according to current flow diagram.
       Specification: ∞ω
• ‒ Additionally check wires for short to battery positive.
       Specification: ∞ω

If no fault in wire is detected:

• ‒ Perform resistance measurement at coolant temperature sender -G62- contacts 1+3 resistance figures => Page 24-12 , Fig.1

If the specification is not attained:

• ‒ Replace coolant temperature sender (G62).

If the specification is attained:

• ‒ Replace Motronic control unit (J220)
  => Page 24-5 , item 3 .