Volkswagen Workshop Service and Repair Manuals

Special tools, tester 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 1598/18
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adaptor 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 at idling. .

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

• ‒ Input 02 for "Display group number" and confirm with Q.

Note:

If something different is indicated on display:

=> Fault reader operating instructions

Functional check of sender.

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

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

Continuation of check when display = 5°C:

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

• ‒ → Pull 4 pin connector off Duo sensor (G71) + (G72) -2-.

• ‒ → Check wiring between test box and 4 pin connector for open circuit according to current flow diagram.
       Contact 1 + socket 17
       Contact 2 + socket 43
       Contact 3 + socket 37
       Contact 4 + socket 18
       Wire resistance: max. 1.5 ω
• ‒ Check wire between control unit connector and 4 pin connector contact 5 for short and to vehicle earth, according to current flow diagram.
       Contact 1 + socket 18
       Contact 1 + socket 37
       Contact 1 + socket 43
       Contact 2 + socket 18
       Contact 2 + socket 37
       Contact 3 + socket 18
       Specification: ∞ ω
• ‒ Additionally check wiring for short to battery positive.
       Specification: ∞ ω

If no fault in wire is detective:

• ‒ Perform resistance measurement on intake air temperature sender (G72) contact 1 + 2, resistance figures => Page 24-12 Fig. 2 .

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 .

Continuation of check when display = ambient temperature

• ‒ → Remove Duo sensor (G71) + (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 ⇒ key.
• ‒ Input 06 for "End output" and confirm with Q.