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, 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 1551/3A

Test conditions

• ● Coolant temperature must be at least 80 °C, =>display group 04, display zone 3.

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 5 for "Display group number 5" and confirm entry with Q key.

• ‒ Check whether the control unit recognises the operating mode (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

Note:

Below 1400 rpm idling speed will be recognised.

• ◆ Part throttle:

• ‒ Rev up evenly.

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

• ◆ Enrichment:

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

• Acceleration 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.

Observe the valid safety precautions when carrying out a road test => Page 24-29 .

• ‒ 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 01-18 , interrogating and erasing fault memory.
• ‒ Check throttle valve control part
  => Page 24-46 .
• ‒ Check parts of the electronic throttle control (EPC) for ease of movement:

=> Repair group 20; Electronic throttle control (EPC); Servicing parts of the electronic throttle control (EPC)