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

Note:

If an engine is brought to operating temperature with the vehicle stationary, and due to unfavourable conditions the time taken to reach operating temperature is too long, it can lead to fault code P0116 or P0125 being stored in fault memory. In this case it is advisable to erase fault memory and bring engine to operating temperature during a test drive.

Test conditions

• ● Engine cold

Test sequence

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit with the "Address word" 01. When doing this the ignition must be switched on.
  (Connecting fault reader and selecting engine electronics control unit .)

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0, 0 and 1 for "Display group number 1" and confirm entry with Q key.

• ‒ Check the specification for coolant temperaturesender (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/open circuit.

Continuation:

• ‒ Start engine and run at idling speed.
  The temperature value must
       increase uniformly

If the specification is not obtained:

• ‒ Replace coolant temperature sender (G62).
• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
• ‒ Switch off ignition.

Notes:

• ◆ Display on fault reader jumps by 1.5 °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.

Evaluating display group 1

Checking wiring

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

• ‒ → Pull 4 pin connector -1- off 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 33
       Contact 3+socket 14
       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.
       Contact 3+socket 33
       Contact 3+vehicle earth
       Specification: ∞ω
• ‒ Additionally check both 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).
• ‒ Read-out the readiness code=> Page 01-34 .