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Checking exhaust gas recirculation - Vehicles as of 08.99 > < Exhaust gas recirculation connection diagram - engine codes ALH, AHF, ASV

A3 Mk1

4-cyl. Diesel Direct Injection Engine (TDI), Mech. Components
Exhaust gas recirculation system
Checking exhaust gas recirculation - Vehicles up to 07.99

The operation of the exhaust gas recirculation system is tested by measuring the intake air mass. If the exhaust gas is being recirculated the proportion of fresh air detected by the air mass meter is lower. The larger the quantity of recirculated exhaust gas, the lower the signal from the air mass meter.
 
W00-0706

Special tools and workshop equipment required

  • ◆ VAS 5051 with VAS 5051/1

Test requirements:

  • ● Vehicle diagnostic, testing and information system VAS 5051 connected, vehicle self-diagnosis and vehicle system "01 - Engine electronics" selected.
  • ● Engine running at idling speed
  • ● Coolant temperature at least 80 °C=> display group 001, display zone 4.
  • ● Final control diagnosis has been performed
 
A01-0122

Test sequence

→ Display on VAS 5051:

  • ‒ Under -1- select the diagnostic function "08 - Read measured value block".
 
A01-0130

→ Display on VAS 5051:

  •     1 -    Enter display group
    max. input value = 255
  • ‒ Enter "003" for "display group number 003" in zone -2- and confirm the entry by pressing the Q button.
  • ‒ Briefly depress the accelerator pedal, then allow the engine to continue running at idling speed.

Display zones

1

2

3

4

Display group 003: Exhaust gas recirculation at idle

Display

xxxx rpm

xxx mg/stroke

xxx mg/stroke

xx %

Display

Engine speed

Air mass (specified)

Air mass (actual)

Checking actuation of EGR valve -N18

Specified value

860...940 rpm

230...370 mg/stroke

210...390 mg/stroke

30...80 %

Note:

If a value higher than 370 mg/stroke is displayed: Engine too cold => run until warm

If specified value is not attained: Evaluation

Evaluation of display group 003

Display zone: 3

Possible causes of fault

Fault remedy

Constant

- Open circuit in wiring to air mass meter

- Testing air mass meter

425 mg/stroke

- Air mass measured not plausible

=> Diesel Direct Injection and Glow Plug System (4-cyl TDI) > 07.99; Repair group 23

Over

- Engine has been running for 10 min at idling speed

- Briefly depress accelerator sharply

390 mg/stroke

- Excessive exhaust gas recirculation

- Checking mechanical exhaust gas recirculation valve => Page 26-33

- Engine load from ancillaries

- Eliminate load (AC system/power steering/alternator)

- Intake manifold temperature too high

- Injection pump too lean

=> Diesel Direct Injection and Glow Plug System (4-cyl TDI) > 07.99; Repair group 01

Less than

- Unmetered air in intake area

- Check intake are for leaks

210 mg/stroke

- Excessive exhaust gas recirculation

- Checking mechanical exhaust gas recirculation valve => Page 26-33

Checking exhaust gas recirculation - Vehicles as of 08.99 > < Exhaust gas recirculation connection diagram - engine codes ALH, AHF, ASV