audi Workshop Repair Guides

Audi Workshop Service and Repair Manuals

ABOUT US
Check lambda probe ageing of lambda probe before catalytic converter > < Function of lambda control

A4 Mk1

Motronic Fuel Injection and Ignition System (6-cylinder)
Checking lambda control
Checking lambda probe and lambda control upstream of catalytic converter
 
G24-0021

Special tools and workshop equipment required

  • ◆ V.A.G 1526 A
  • ◆ V.A.G 1594 A
  • ◆ V.A.G 1598/31
  • ◆ VAS 5051 with VAS 5051/1
  • or
  • ◆ V.A.G 1551 with V.A.G 1551/3 A

Notes:

  • ◆ For specific fault search, it is possible to switch off the lambda control by selecting display group 099 under "Basic setting" mode and to switch it on again with "Read measured value block".
  • ◆ After selecting the display group 099 (whether in "Basic setting" or "Read measured value block" mode), it is possible to switch back and forth between the functions 04 "Basic setting" and 08 "Read measured value block" by pressing the keys 4 or 8 on V.A.G 1551.
  • ◆ On leaving function 04 "Basic setting", the lambda control is automatically re-activated.

Test requirements:

  • ● Test drive performed and fault memory not erased.
  • ● Coolant temperature at least 80 °C=> display group 004, display zone 3.

Functional test

  • ‒ Connect vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit with "Address word" 01
    For this purpose, the engine must be running at idle speed
 
→ When indicated on display:
Rapid data transfer     HELP
Select function XX
  • ‒ Enter "04" to select "Start basic setting" and confirm with Q key.

Note:

During basic setting, the solenoid valve for the active carbon canister (valve -N80) is closed and the air conditioner compressor is switched off.
 
→ When indicated on display:
Basic setting      Q
Enter display group number XXX
  • ‒ Enter "030" for "display group number 030" and confirm entry with Q key.
 
→ When indicated on display:
System in basic setting 30    ⇒
    1    2    3    4
  • ‒ Check lambda probe status in display zones 1 to 3.

Note:

The "lambda probe status" indicates the condition of the lambda control and the lambda probes.

Display zones

1

2

3

4

Display group 030: Lambda status at idle

Display

X X X

X X X

X X X

X X X

Display

Lambda probe status, Bank 1, probe 1

Lambda probe status, Bank 2, probe 1

Lambda probe status, Bank 2, probe 1

Lambda probe status, Bank 2, probe 2

Range

0 = off
1 = on

0 = off
1 = on

0 = off
1 = on

0 = off
1 = on

Specified value

1 1 1

1 1 0

1 1 1

1 1 0

Note

If specified value not attained

Significance of 3-digit readout of display group 030

X

X

X

Display zones 1...4

X

Lambda control 0 = not active, 1 = active

X

Operational readiness of lambda probe 0 = not active, 1 = active

X

Condition of lambda probe heating: 0 = not active, 1 = active

Notes:

  • ◆ The first digit of the 3-digit display (heating) fluctuates between 0 and 1 at certain operating points.
  • ◆ The lambda control of lambda probe after catalytic converter (bank 1, probe 2 and bank 2, probe 2) is not active without engine load, i.e. the display of the 3-digit display is 0.

Checking lambda probe learned values and lambda control

  • ‒ Press Ckey.
 
→ When adjacent display appears:
Basic setting      Q
Enter display group number XXX
  • ‒ Enter "033" for "display group number 033" and confirm entry with Q key.
 
→ When adjacent display appears:
System in basic setting 33    ⇒
    1    2    3    4
  • ‒ Check specified values in display zones 1 and 3.

1

2

3

4

Display group 033: Lambda control upstream of catalytic converter

Display

xx.x %

x.xxx Volt

xx.x %

x.xxx V

Display

Lambda control
Bank 1

Lambda probe voltage Bank 1

Lambda control
Bank 2

Lambda probe voltage Bank 2

Range

-25.0...25.0 %

0.100...1.000 V

-25.0...25.0 %

0.100...1.000 V

Specified value

In range -10.0...10.0 % value must fluctuate at least 2 %

In range from 0.100...1.000 Volt, the voltage must fluctuate by approx. 0.3 V

In range -10.0...10.0 % value must fluctuate at least 2 %

In range from 0.100...1.000 Volt, the voltage must fluctuate by approx. 0.3 V

Note

If specified value not attained

If specified value not attained

Interpreting display group 033

Display zone: 1 / 3

Possible causes of fault

Fault remedy

Values in range:
-10.0...-25.0 %

- Lambda probe heating defective

- Check lambda probe heating

or
Values in range:

- Open circuit between lambda probe and control unit

- Check basic voltage => Page 24-92

10.0...25.0 %
or
Value does not fluctuate by at least 2%

- Short to earth or positive between lambda probe and control unit

- Check lambda probe wiring Bank 1 lambda probe 1 => Page 24-94

- Unmetered air in intake area

- Check intake system for leaks and rectify unmetered air

- Fuel system pressure too high or too low

- Check fuel pressure regulator

- Fuel retardation pipe bent or clogged

- Check fuel retardation pipe
  • ‒ Press Ckey.
  • ‒ Enter "032" for "display group number 032" and confirm entry with Q key.
 
→ When indicated on display:
System in basic setting 32    ⇒
    1    2    3    4
  • ‒ Check lambda control in display zones 1 to 4:

Display zones

1

2

3

4

Display group 032: Lambda learned values upstream of catalytic converter

Display

xx.x %

xx.x %

xx.x %

xx.x %

Display

Lambda learned value
Bank 1 at idle
(additive)

Lambda learned value, Bank 1, at part load
(multiplicative)

Lambda learned value
Bank 2 at idle
(additive)

Lambda learned value Bank 2 at part load
(multiplicative)

Range

-25.0...25.0 %

-25.0...25.0 %

-25.0...25.0 %

-25.0...25.0 %

Specified value

-10.0...10.0 %
can fluctuate slightly

-10.0...10.0 %
can fluctuate slightly

-10.0...10.0 %
can fluctuate slightly

-10.0...10.0 %
can fluctuate slightly

Note

If specified value not attained

Interpreting display group 032

Display zone:
1 / 3 or 2 / 4

Possible causes of fault

Fault remedy

Lambda learned values in range
-10.0...-25.0 %

- Oil dilution

- Carry out oil change or drive vehicle fairly fast on out-of-town roads

- High oil consumption

- Air mass meter defective

- Test air mass meter

- Solenoid valve for active carbon canister stuck open

- Check solenoid valve for activated charcoal canister .

- Fuel pressure too high

- Check fuel pressure regulator

- Fuel retardation pipe bent or clogged

- Check fuel retardation pipe

- Injector not closing

- Check injectors

Interpreting display group 032

Display zone:
1 / 3 or 2 / 4

Possible causes of fault

Fault remedy

Lambda learned values in range
10.0...25.0 %

- Unmetered air in intake area

- Check intake system for leaks and rectify unmetered air
.

- Fuel pressure too low

- Check fuel pressure regulator

- Air mass meter defective

- Test air mass meter

- Lambda probe heating defective
- Lambda probe defective

- Check lambda probe heating

- Injector only opens partially or not at all

- Check injectors

- Activated charcoal filter system solenoid valve sticking

- Check solenoid valve for activated charcoal canister

- Ignition coil/spark plug defective

- Check ignition coils => Page 28-7

Checking basic voltage

Fitting location of connectors => Installation position overview Page 24-5

Test requirements:

  • ● Fuse for Lambda probes OK.

=> Current Flow Diagrams, Electrical Fault-Finding and Fitting Locations

  • ‒ Disconnect 4- pin connector to relevant Lambda probe.
 
A24-0013
  • ‒ → Connect multimeter between contacts 3 and 4 to measure voltage.
  • ‒ Switch the ignition on.
    • ‒ Specified value: 0.400...0.500 V
  • ‒ Switch ignition off.

If specified value is not attained:

  • ‒ Check the Lambda probe lines
    => Bank 1 Page 24-94

Check lambda probe wiring Bank 1 lambda probe 1 upstream of catalytic converter -G39

Fitting location of connectors => Installation position overview Page 24-5

  • ‒ Unplug 4-pin connector for bank 1, lambda probe 1 -G39.
  • ‒ Connect the V.A.G 1598/31 test box to wiring harness leading to engine control unit; the engine control unit should not be connected => Page 24-17.
 
A24-0013
  • ‒ → Test for open circuit in the following wiring connections.

Connector
contact

Test box V.A.G 1598/31
Socket

3

51

4

70
  • ‒ Rectify open circuit, if necessary
  • ‒ Check for shorts between the two lines.

Connector
contact

Test box V.A.G 1598/31
Socket

4

51
 
A24-0013
  • ‒ → Test screen wiring for short to Lambda probe wiring.

Connector
contact

Test box V.A.G 1598/31
Socket

3

32

4

32

If no wiring fault is detected:

  • ‒ Fit a new engine control unit => Page 24-22.

Checking lambda probe wiring bank 2 lambda probe 1 upstream of catalytic converter -G108

Fitting location of connectors => Installation position overview Page 24-5

  • ‒ Unplug 4-pin connector for bank 2, lambda probe 1 -G108.
  • ‒ Connect the V.A.G 1598/31 test box to wiring harness leading to engine control unit; the engine control unit should not be connected => Page 24-17.
 
A24-0013
  • ‒ → Test for open circuit in the following wiring connections.

Connector
contact

Test box V.A.G 1598/31
Socket

3

12

4

13
  • ‒ Rectify open circuit, if necessary
  • ‒ Check for shorts between the two lines.

Connector
contact

Test box V.A.G 1598/31
Socket

4

12
  • ‒ Test screen wiring for short to lambda probe wiring.

Connector
contact

Test box V.A.G 1598/31
Socket

3

32

4

32

If no wiring fault is detected:

  • ‒ Fit a new engine control unit => Page 24-22.

Check lambda probe ageing of lambda probe before catalytic converter > < Function of lambda control