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 electronics 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

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

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.
• ‒ Switch off ignition

Continuation of check when display = 77.7 °C:

• ‒ → 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 14
       Contact 3+socket 33
       Wire resistance: Max. 1.5 ω
• ‒ Check wire 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 24-20 , Fig. 1

If the specification is not obtained:

• ‒ Replace coolant temperature sender (G62).