volkswagen Workshop Repair Guides

Volkswagen Workshop Service and Repair Manuals

Checking Lambda probe and Lambda regulation before catalyst > < Checking functions
4LV injection and ignition system
Checking functions
Idling check

Notes:

  • ◆ Idling speed, ignition timing and CO content not adjustable.
  • ◆ The idling speed is regulated to specification by the throttle valve positioner in conjunction with the DIS function.
  • ◆ CO content regulated by Lambda regulation. Faults in Lambda control are detected in self-diagnosis and stored in fault memory.

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 1551/3

Check conditions

  • ● Exhaust system between cylinder head and catalyst free of leaks
  • ● Coolant temperature must be at least 80 °C, =>display group 04, display zone 3.
  • ● 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.
  • ● On vehicles with automatic gearbox selector lever in "P" or "N" position

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 .)
  • ‒ Interrogate fault memory, if necessary, repair fault and then erase fault memory.
    => Page 01-16 , interrogating and erasing fault memory
  • ‒ Then:
    • ‒ Leave fault reader V.A.G 1551 connected.
    • ‒ Continue running engine at idling speed.
 
→ Indicated on display:
Rapid data transfer     HELP
Select function XXX

Checking idling speed

  • ‒ Press keys 0, 5 and 6 for "Display group number 56" and confirm entry with Q key.
 
→ Indicated on display:
(1...4 = Display zones)
Read measured value block     56     ⇒
     1     2     3     4    
  • ‒ Check the operating mode in display zone 4
         Specification: 00000
    (Significance => Page 01-133 )
  • ‒ Check the specified idling speed in
    display zone 2.
         Specification:
         Vehicles with engine code AUA
         850 rpm
         Vehicles with engine code AUB
         840 rpm
         Vehicles with automatic gearbox
         680 rpm

Note:

The specified engine speed is increased when battery is heavily discharged or engine has overheated.

  • ‒ Check idling speed in display zone 1.
         Specification:
         Vehicles with engine code AUA
         800...900 rpm1)
         Vehicles with engine code AUB
         790...890 rpm1)
         Vehicles with automatic gearbox
         630...730 rpm1)

     1)     Up-to-date specifications:

=> Exhaust emissions test binder

  • ‒ Press ⇒key.
  • ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.

If the idling speed is not obtained:

  • ‒ Adapt the engine control unit to the throttle valve control part => Page 24-123
  • ‒ Carry out test drive.
  • ‒ Again interrogate the control unit fault memory.
  • ‒ Repeat the idling check.

If the specifications are not obtained again:

  • ‒ Check throttle valve control part
    => Page 24-43 .
  • ‒ Check the operating condition of engine
    => Page 24-109 .
  • ‒ Check the intake air system for unmetered air
    => Page 24-85

Checking Lambda probe and Lambda regulation before catalyst > < Checking functions