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).

Notes:

• ◆ Only gold-plated contacts may be used when servicing the throttle valve control part connector contacts.

If the throttle valve control part is replaced, the following must be carried out:

• ◆ Erase learnt values and adapt engine control unit to the throttle valve control part .

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/3
• ◆ Adapter set V.A.G 1594
• ◆ Test box V.A.G 1598/31
• ◆ Current flow diagram

Check conditions

• ● The battery voltage must be at least 11.5 V.
• ● All electrical consumers, e.g. lights and rear window heating must be switched off.
• ● If the vehicle is equipped with an air conditioning system, this must be switched off.
• ● 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 01-10 .)

• ‒ 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 sender 1 (G187) at idling speed limit stop in display zone 1
       Specification: 0.0...100.0 %
• ‒ Check throttle valve angle sender 2 (G188) at idling speed limit stop in display zone 2
       Specification: 100.0...0.0 %
• ‒ Depress accelerator slowly to full throttle position and observe angles displayed in display zones 1 and 2:

• The percentage in display zone 1 must rise
       evenly.
  The tolerance range 0.0...100.0 % is never used completely.
• The percentage in display zone 2 must fall
       evenly.
  The tolerance range 100.0...0.0 % is never used completely.

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 24-26 , Fig. 2 .

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

• ‒ → Measure the resistance on throttle valve control part between the contacts 3 + 5
       Specification: 1.0...5.0 ω(at room temperature)

If the specification is not obtained:

• ‒ Replace throttle valve control part
  => Page 24-18 , item 7 .
• ‒ Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page 01-20 , interrogating and erasing fault memory.
• ‒ Erase the learnt values and adapt the engine control unit again=> Page 24-128 .

If the specification is obtained:

• ‒ Check voltage supply of throttle valve control part and wiring to control unit => Page 24-47 .
• ‒ 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 24-121 .

Checking voltage supply and wiring to control unit

• ‒ → Connect multimeter to measure voltage at connector contacts 2 (positive) + 6 (earth).
• ‒ Switch on ignition.
       Specification: min. 4.5 V
• ‒ Switch off ignition.

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

If the specifications are not attained:

• ‒ → Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.

• ‒ → Check wiring for open circuit between test box and connector referring to current flow diagram:
       Contact 1 and test box socket 90
       Contact 2 and test box socket 97
       Contact 3 and test box socket119
       Contact 4 and test box socket 92
       Contact 5 and test box socket121
       Contact 6 and test box socket 91
       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 24-117 .