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
• ◆ Chilling spray (commercially available)

Test sequence

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit (address word 01); carry out selection with ignition switched on.
  

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

• ‒ Enter 03 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

• ‒ Note intake air temperature figure in display zone 4.

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

Continuation of check when display shows 19.6 °C:

• ‒ Switch off ignition

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

• ‒ → Pull 2 pin connector -1- off intake air temperature sender (G72) -2-.

• ‒ → Check wiring between test box and 2 pin connector for open circuit according to current flow diagram.
       Contact 1+socket 36
       Contact 2+socket 33
       Wire resistance: Max. 1.5 ω
• ‒ Check wire between control unit connector and 2 pin connector contact 2 for short to wire contact 1 and to vehicle earth, according to current flow diagram.
       Contact 2+socket 36
       Specification: ∞ω
• ‒ Additionally check wiring for short to battery positive.
       Specification: ∞ω

If no fault in wire is detected:

• ‒ Perform resistance measurement on intake air temperature sender (G72) contacts 1+2, resistance figures => Page 24-20 , Fig. 1

If the specification is not obtained:

• ‒ Replace intake air temperature sender (G72)

Continuation of check when display = ambient temperature:

• ‒ → Remove intake air temperature sender (G72) (plug remains connected).
• ‒ Note intake air temperature figure in display zone 4.
• ‒ Spray sender with a commercial chilling spray and at the same time observe the temperature figure. The temperature figure must
       decrease.
• ‒ Press ⇒ button.
• ‒ Input 06 for "End output" and confirm with Q.