Volkswagen Workshop Service and Repair Manuals

Special tools, testers, measuring instruments and auxiliary items required

• ◆ 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 the fault reader V.A.G 1551 (V.A.G 1552). Then switch ignition on and select engine control unit with the "Address word" 01.
  (Connecting fault reader and selecting engine 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 2 for "Display group number 2" and confirm entry with Q key.

• ‒ Read off intake air temperature value in display zone 4.

     1)     If a temperature is displayed which is below the ambient air temperature of the sender, check sender wiring for transfer resistances. Note when doing this that sender is heated from external sources, e.g. radiated heat when engine is not running.

Continuation of check when display -40 °C:

• ‒ → Pull connector -1- off intake air temperature sender (G42) with intake manifold pressure sender (G71) -2-.
• ‒ Bridge connector contacts 1+2 using aux. cables from V.A.G 1594 and observe display.

Display 129 ° C:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Renew intake air temperature sender (G42) with intake manifold pressure sender -2-
  , item 1 .

Display -40 ° C:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.

• ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.
• ‒ Check wire between test box socket 43 and 4 pin connector contact 2 for open circuit according to current flow diagram.
       Wire resistance: Max. 1.5 ω
• ‒ Check wiring additionally for short circuit to battery positive.
       Specification: ∞ω
• ‒ Check wire between test box socket 17 and 4 pin connector contact 1 for open circuit according to current flow diagram.
       Wire resistance: Max. 1.5 ω

If no fault in wire is detected:

• ‒ Renew engine control unit
  => Page 24-11 , item 28

Continuation of check when display 129 °C:

• ‒ → Pull connector -1- off intake air temperature sender (G42) with intake manifold pressure sender (G71) -2-.

Display -40 ° C:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Renew intake air temperature sender (G42) with intake manifold pressure sender -2-
  , item 1 .

Display 129 ° C:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Pull connector off engine control unit.
• ‒ Check wiring to control unit connector at 4 pin connector contact 2 for short to wire contact 1 and to vehicle earth.
       Specification: ∞ω

If no wiring fault is detected:

• ‒ Renew engine control unit
  => Page 24-11 , item 28

Continuation of check when display = ambient temperature:

• ‒ → Remove intake air temperature sender together with intake manifold pressure sender (connector remains connected).
• ‒ Note intake air temperature value in display zone 4.
• ‒ Spray sender with commercial chilling agent whilst observing the temperature value. The temperature value must
       decrease.
• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.