Volkswagen Workshop Service and Repair Manuals

Note:

Check whether engine control unit recognises the engine operating modes (idling speed, part throttle, full throttle, overrun).

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 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 .)

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

• ‒ Press keys 0, 0 and 4 for "Display group number 4" and confirm entry with Q key.

• ‒ Observe -8 digit number block- in display zone 4 :
  (The right-hand 4 digits are of no consequence)

Display in operating mode

• ◆ Idling:

• 2nd position from left must display 1
       Display: 01000000

• ◆ Part throttle:

• ‒ Rev up evenly.

• 3rd position from left must display 1
       Display:: 00100000

• ◆ Full throttle:

• ‒ Briefly open throttle fully (throttle burst).

• 4th position from left must briefly display 1
       Display: 00010000

• ◆ Overrun mode:

• ‒ Increase engine speed to above 3000 rpm.
• ‒ Close throttle valve abruptly.

• As long as the engine speed is above 1200 rpm 1st position from left must display 1
       Display: 11000000 (briefly)

Note:

Below 1200 rpm idling speed is again recognised.

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

If the specifications are not attained:

• ‒ Interrogate fault memory, if necessary, repair fault and erase fault memory.
  => Page 01-6 , interrogating and erasing fault memory
• ‒ Check throttle valve potentiometer
  => Page 24-32 , Checking throttle valve control part.