Volkswagen Workshop Service and Repair Manuals

Components of throttle valve control part (J338):
Throttle valve drive (G186), angle sender 1 for throttle valve drive (G187) and angle sender 2 for throttle valve drive (G188).

Note:

If the throttle valve control part is replaced, the new control part must without fail be adapted to the engine control unit .

Special tools, workshop equipment, 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 1551/3A
• ◆ Test box V.A.G 1598/22
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Check conditions

• ● Coolant temperature must be at least 80 °C, =>display group 04, display zone 3.

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 01-9 .)

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0, 6 and 2 for the "Display group number 62" and confirm entry with Q key.

• ‒ Check throttle valve angle at idling stop from sender 1 (G187) in display zone 1
       Specification: 10...90 %
• ‒ Check throttle valve at idling stop from sender 2 (G188) in display zone 2.
       Specification: 90...10 %
• ‒ Depress accelerator slowly to full throttle position and observe angles displayed in display zones 1 and 2:

• The percentage figure in display zone 1 must increase evenly. Although the tolerance range 10...90 % will not be fully exploited.
• The percentage figure in display zone 2 must decrease evenly. Although the tolerance range 90...10 % will not be fully exploited.

Notes:

• ◆ The reason why the display in display zone 1 increases and the display in display zone 2 decreases is because the potentiometers (angle senders) in the throttle valve control part run in opposite directions.
• ◆ This means that the voltage of one angle sender moves towards 5 volts. (The more the throttle valve is opened the higher the voltage; percentage figure increases).

• ◆ Whilst the voltage of angle sender 2 decreases from 5 volts towards 0 volts. (The more the throttle valve is opened the lower the voltage; percentage figure decreases).

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

If the displays do not indicate as described:

• ‒ Remove air cleaner => Page 24-27 , Fig. 3 .

• ‒ → Pull 6-pin connector off throttle valve control part -arrow-.

• ‒ → Measure resistance at throttle valve drive between contacts 3 + 5
       Specification: 1.0...5.0 ω

If the specification is not obtained:

• ‒ Replace throttle valve control part
  => Page 24-17 , item 7 .
• ‒ Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page 01-18 , interrogating and erasing fault memory.
• ‒ Adapt engine control unit to throttle valve control part => Page 24-141 .

If the specification is obtained:

• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-51 .
• ‒ Check the accelerator pedal position sender.

=> Repair group 20; Electronic engine output regulation (electronic accelerator (EPC)); Checking accelerator pedal position sender

If the voltage supply and wiring is OK:

• ‒ Replace engine control unit
  => Page 24-135 .

Checking voltage supply and wiring to control unit

Test conditions

• ● The battery voltage must be at least 11.5 V.

Test sequence

• ‒ → Connect Multimeter to measure voltage at connector contacts 2 + 6.
• ‒ Switch on ignition.
       Specification: min. 4.5 V
• ‒ Switch off ignition.

• ‒ → Connect Multimeter to measure voltage at connector contact 2 and earth.
• ‒ Switch on ignition.
       Specification: min. 4.5 V
• ‒ Switch off ignition.

If the specifications are not attained:

• ‒ Remove wiper arms and cowl panel:

=> Electrical system; Repair group 92; windscreen wiper system; removing and installing windscreen wiper system

• ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness.

• ‒ → Check wires between test box and 6-pin connector (connector to control unit) for open circuit using current flow diagram.
       Contact 1+socket 68
       Contact 2+socket 55
       Contact 3+socket 80
       Contact 4+socket 75
       Contact 5+socket 66
       Contact 6+socket 61
       Wire resistance: max. 1.5 ω
• ‒ Additionally check wires for short to one another, to vehicle earth and to battery positive.
       Specification: ∞ω

If no fault is detected in the wiring:

• ‒ Check engine control unit voltage supply => Page 24-129 .