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Checking needle lift sender > < Checking engine speed sender -G28

A4 Mk1

TDI diesel injection and glow plug system (4-cyl.) 08.99 ä
Checking control unit input values
Checking air mass meter -G70

The signal from the air mass meter is required by the control unit to calculate the required injection quantity and to control the exhaust gas recirculation. The weaker the signal from the air mass meter, the less fuel can be injected.

Important:
Secure fault reader to rear seat and operate from this location. When doing this, always observe the relevant safety precautions .
  • ‒ Read measured value block, Display Group 10, engine running at idling speed => Page 01-89
 
→ Indicated on display:
Read measured value block 10    ⇒
    309 mg/H    1030 mbar    1011 mbar    0.0 %
  • ‒ Observe display in display zone 1.
 
→ Specification: 230...370 mg/H (mg/stroke)
Read measured value block 10    ⇒
    309 mg/H    1030 mbar    1011 mbar    0.0 %

If the specification is not obtained:

  • ‒ Check exhaust gas recirculation:

=> 4-Cyl. Diesel Direct Injection Engine (TDI), Mechanics; Repair Group 26; Testing exhaust gas recirculation system

If the specification is obtained:

  • ‒ Accelerate vehicle from approx. 1500 rpm at full throttle; in second gear for manual gearbox or second driving range for automatic gearbox.
  • ‒ Press PRINT key on V.A.G 1551 at approx. 3000 rpm. The accelerator pedal must be fully depressed at this moment in time.
 
→ Specification for display zone 4: 100 % (accelerator pedal position)
Read measured value block 10    ⇒
    830 mg/H    1030 mbar    1850 mbar    100 %

If the specification is not obtained:

  • ‒ Repeat test and accelerate vehicle at full throttle.
 
→ Specification for display zone 3: (charge pressure)
Read measured value block 10    ⇒
    830 mg/H    1030 mbar    1850 mbar    100 %
  • Engine code AFF, AHU, AHH:
    1800...2050 mbar
  • Engine code AFN, AVG:
    1800...2250 mbar

    • If the specification is not obtained:

    • ‒ Test charge pressure

    => 4-Cyl. Diesel Direct Injection Engine (TDI), Mechanics; Repair Group 21; Testing charge pressure system
     
    → Specification for display zone 1: intake air mass
    Read measured value block 10    ⇒
        830 mg/H    1030 mbar    1850 mbar    100 %
  • Engine code AFF, AHU, AHH:
    > 750 mg/H (mg/stroke)
  • Engine code AFN, AVG:
    > 800 mg/H (mg/stroke)

    • If the specification is not obtained:

    • ‒ Renew air mass meter (G70).

    If display zone 1 shows a fixed substitute value:

    • ‒ Switch off ignition.
    • ‒ Disconnect connector for air mass meter
      =>Fitting locations overview, Page 23-4.
    • ‒ Switch ignition on.
     
    A23-0058
    • ‒ → Connect hand-held multimeter (voltage range) between the following contacts on the connector:

    5-pin connector on wiring harness, contact

    Specification

    2 + earth

    Battery voltage

    2 + 3

    Battery voltage

    4 + earth

    approx. 5 V

    4 + 3

    approx. 5 V

    If the specifications are not obtained:

    • ‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
      => Page 23-47.
     
    A23-0058

    The following wiring connections are to be checked for open circuits and/or short to positive or negative.

    5-pin connector on wiring harness, contact

    Test box V.A.G 1598/31, socket

    1

    -

    2

    1 and 2

    3

    49

    4

    30

    5

    68
    • ‒ Rectify any open/short circuit as necessary.

    => Current flow diagrams, Electrical fault finding and Fitting locations binder

    Checking needle lift sender > < Checking engine speed sender -G28