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
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Test box V.A.G 1598/18
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test sequence

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
  (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 3 for "Display group number 3" and confirm entry with Q key.

• ‒ Read off the displayed value for engine load in display zone 2 and note this value.
• ‒ Briefly open throttle valve. The engine load value must increase briefly.

If the display shows constantly 0 % or 100 %:

Continuation of check when display 0%:

• ‒ → Pull connector -1- off intake manifold pressure sender (G71) with intake air temperature sender (G42) -2- (engine stops).
• ‒ Bridge connector contacts 3+4.

Display 100 %:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Renew the intake manifold pressure sender (G71) with intake air temperature sender (G42) -2-
  => Page 24-13 , item 1 .

Display 0 %:

• ‒ 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 wiring between test box and connector for open circuit according to current flow diagram.
       Contact 3+socket 37
       Contact 4+socket 18
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wiring contact 4 for short to earth and to contact 1.
       Specification: ∞ω

If no wiring fault is detected:

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

Continuation of check when display 100 %:

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

Display 0 %:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Renew the intake manifold pressure sender (G71) with intake air temperature sender (G42) -2-
  => Page 24-13 , item 1 .

Display 100 %:

• ‒ Press the ⇒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 4 for short to wire contact 3 and to battery positive.
       Specification: ∞ω

If no wiring fault is detected:

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