Volkswagen Workshop Service and Repair Manuals

Note:

If the throttle valve control part (J338) is removed and installed or replaced the basic setting must be performed .

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

Checking idling switch

• ‒ 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 => Page 01-4 .)

• ‒ 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.

• ‒ Observe 8 digit number block in display zone 4 :

• 4th position from left with closed throttle valve must display 0
       Display: 00000000

• ‒ Slowly open throttle valve. After free travel, a stop is reached when opening throttle valve further the 4th position from left must jump to 1
       Display: 00010000

If the specifications are not obtained:

• ‒ Remove air cleaner => Page 24-18 , Fig. 2 .

Continuation of check when display is always at 1

• ‒ → Detach connector -1- from throttle valve control part -2-.
• ‒ Bridge connector contacts 3+7 with aux. cables from V.A.G 1594 and observe display.

Display 0:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Replace throttle valve control part
  , item 4 .

Display 1:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-45 .

If the voltage supply and wiring is OK:

• ‒ Renew engine control unit
  => Page 24-11 , item 30

Continuation of check when display constantly shows 0

• ‒ → Detach connector -1- from throttle valve control part -2-.

Display 1:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Replace throttle valve control part
  , item 4 .

Display 0:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-45 .

If the voltage supply and wiring is OK:

• ‒ Renew engine control unit
  => Page 24-11 , item 30

Checking throttle valve positioner and throttle valve positioner potentiometer

Test conditions

• ● Coolant temperature at least 80 °C

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 => Page 01-4 .)

• ‒ 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.

• ‒ Check voltage value for throttle valve positioner potentiometer throttle valve opening in display zone 4. The voltage must be
       approx. 4 V

If the specification is not obtained:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Remove air cleaner => Page 24-18 , Fig. 2 .

• ‒ → Detach connector -1- from throttle valve control part -2-.
• ‒ Measure throttle valve positioner resistance between connector contacts 1+2.
       Specification: 3...200 ω
• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-45 .

If no fault is detected:

• ‒ Replace throttle valve control part
  , item 4 .

Checking throttle valve potentiometer

Test conditions

• ● Coolant temperature at least 80 °C

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 => Page 01-4 .)

• ‒ 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 throttle valve angle in display zone 3.
• ‒ Slowly open throttle valve fully and observe angle display in display zone 3. The figure must increase uniformly over
       the complete range.
• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.

If the figure does not increase uniformly:

• ‒ Replace throttle valve control part
  , item 4 .

If the display constantly shows 0 <° or is above 90 <°:

• ‒ Remove air cleaner => Page 24-18 , Fig. 2 .

Continuation of check when display 0 <°:

• ‒ → Detach connector -1- from throttle valve control part -2-.
• ‒ Bridge connector contacts 5+7 with auxiliary cables from V.A.G 1594 and observe display.

Display above 90 <°:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Replace throttle valve control part
  , item 4 .

Display 0 <°:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-45 .

If the voltage supply and wiring is OK:

• ‒ Renew engine control unit
  => Page 24-11 , item 30

Continuation of check when display is above 90 <°:

• ‒ → Detach connector -1- from throttle valve control part -2-.

Display 0 <°:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Replace throttle valve control part
  , item 4 .

Display above 90 <°:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-45 .

If the voltage supply and wiring is OK:

• ‒ Renew engine control unit
  => Page 24-11 , item 30

Checking voltage supply and wiring to control unit

• ‒ Remove air cleaner => Page 24-18 , Fig. 2 .
• ‒ → Detach connector -1- from throttle valve control part -2-.
• ‒ Connect multimeter to measure voltage at connector contacts 4+7.
• ‒ Switch on ignition.
       Specification: min. 4.5 V
• ‒ Switch off ignition.
• ‒ Connect multimeter to measure voltage at connector contacts 3+7.
• ‒ Switch on ignition.
       Specification: min. 9 V

• ‒ 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 1+socket 2
       Contact 2+socket 26
       Contact 3+socket 10
       Contact 4+socket 14
       Contact 5+socket 41
       Contact 7+socket 17
       Contact 8+socket 16
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wires for short to one another.
       Specification: ∞ω

If no wiring fault is detected:

• ‒ Check voltage supply of engine control unit => Page 24-61 .