Volkswagen Workshop Service and Repair Manuals

Note:

Checks whether engine control unit recognises the engine operating modes idling, overrun, part throttle, enrichment, full throttle.

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

Check conditions

• ● Coolant temperature at least 85 °C.
• ● Throttle cable adjustment must be OK, checking:

=> Repair group 20; Removing and installing parts of fuel supply system; Adjusting throttle mechanism

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 1 for "Display group number 1" and confirm entry with Q key.

• ‒ Check whether the coolant temperature is above 85 °C in display zone 2.
• ‒ Press the ⇒key.

• ‒ Press keys 0, 0 and 5 for "Display group number 5" and confirm entry with Q key.

Display for operating modes in display zone 4:

• ◆ Idling:

• As long as the engine is running at idling speed idling must be displayed
       Display: Idling

• ◆ Overrun mode:

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

• As long as the engine speed is above 1400 rpm overrun must be displayed
       Display: Overrun

• ◆ Part throttle:

• ‒ Rev up evenly.

• As long as the engine is being revved up evenly, part throttle must be displayed
       Display: Part throttle

• ◆ Enrichment:

• ‒ Quickly increase engine speed.

• Enrichment must be displayed briefly
       Display: Enrichment

• ◆ Full throttle:

• ‒ Floor accelerator pedal (onto throttle valve stop).

• Full throttle must be displayed briefly
       Display: Full throttle

Note:

A test drive may have to be performed to show "Full throttle" in display.

A 2nd person is required when performing a test drive.

• ‒ 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 any faults and then erase fault memory => Page 01-13 , interrogating and erasing fault memory.
• ‒ Check accelerator mechanism for ease of operation.

Vehicles08.95 ▸

• ‒ Check throttle valve potentiometer
  => Page 24-37 , Checking throttle valve control part.

Vehicles ▸07.95

• ‒ Check throttle closing damper and its adjustment => Page 24-91 .