Volkswagen Workshop Service and Repair Manuals

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 85 °C, =>display group 04, display zone 3.
• ● Intake air temperature less than 60°C
  =>display group 04, display zone 4
• ● All electrical consumers, e.g. lights and rear window heating must be switched off
• ● If the vehicle is equipped with an air conditioner, this must be switched off.
• ● On vehicles with automatic gearbox selector lever in "P" or "N" position
• ● Throttle cable adjustment must be OK, checking:

=> Repair group 20; Throttle mechanism; Adjusting throttle cable

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 01-14 , interrogating and erasing fault memory
• ‒ Then:
• ‒ Leave fault reader V.A.G 1551 connected.
• ‒ Continue running engine at idling speed.

• ‒ Press keys 0 and 4 for the function "Introduction of basic setting" and confirm entry with Q key.

• ‒ Press keys 0, 0 and 1 for "Display group number 1" and confirm entry with Q key.

Note:

In the "System in basic setting" function the activated charcoal filter solenoid valve 1 (N80) is closed and the air conditioner compressor switched off.

• ‒ Check the setting conditions for basic settings in display zone 4:
       Specification: 111111
  Significance of figures => Page 01-70
• ‒ Briefly increase engine speed (rev- up) and then allow engine to run at idling speed for 2 minutes.

Checking idling speed

• ‒ Change to display group 56 as follows:
• ‒ Press C key.
• ‒ Press keys 0, 5 and 6 for "Display group number 56" and confirm entry with Q key.

• ‒ Check specified idling speed in display zone 2.
       Specification: 780 rpm1)
• ‒ Check idling speed in display zone 1.
       Specification: 740...820 rpm1)

     1)     Up-to-date specifications:

=> Exhaust emissions test binder

Note:

During idling check the activated charcoal filter solenoid valve and the air conditioner are switched off and the Lambda regulation learning procedure is initiated.

• ‒ 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 24-119
• ‒ 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 24-31 .
• ‒ Check the signals from / to air conditioner
  => Page 24-128 .
• ‒ Check the operating condition of engine
  => Page 24-105 .