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Checking ageing of lambda probes before catalytic converter (on vehicles which conform to emission standard EU III) > < Function of lambda control

A4 Mk1

Motronic Fuel Injection and Ignition System (6-cyl. Turbo)
Checking lambda control
Checking lambda probe and lambda control before 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 vehicles which only fulfil emission standard EU II-D3, one lambda probe is installed per cylinder bank, i.e. a total of 2. For vehicles which fulfil emission standard EU III, two lambda probes are installed per cylinder bank, i.e. a total of 4.
  • ◆ For specific fault search, it is possible to switch off the lambda control by selecting display group 99 "Basic setting" mode and to switch it on again by selecting display group 99 in "Read measured value block" mode.
  • ◆ After selecting the display group 99 (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 conditions

  • ● Perform road test and do not erase fault memory.
  • ● Coolant temperature at least 85 °C (display group 4, display zone 3)

Functional test

  • ‒ Connect the vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select the engine electronics control unit with "address word" 01 .
    For this purpose, the engine must be running at idle speed.
 
→ Indicated on display:
Rapid data transfer     HELP
Select function XX
  • ‒ Press keys 0 and 4 for the function "Introduction of basic setting" and confirm entry with Q key.

Note:

During basic setting, the solenoid valve for the activated charcoal filter (valve -N80) is closed and the air conditioner compressor is switched off.
 
→ Indicated on display:
Basic setting     
Enter display group number XXX
  • ‒ Press keys 0, 3 and 0 for "display group number 30" and confirm entry with Q key.
 
→ Indicated on display:
(1...4 = display zones)
System in basic setting 30    ⇒
    1    2    3    4
  • ‒ Check lambda probe status
    (display zones 1 to 4)

Note:

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

Please note:

On vehicles which do not conform to emission standard EU III, the display zones 2 and 4 remain empty, the "post-catalytic converter control is not active. This also applies for the other tests.

Display zones

1

2

3

4

Display group 30: Lambda status at idle (coolant temperature at least 85 °C)

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

Specification

1 1 1

1 1 0

1 1 1

1 1 0

Note:

Explanation of display=> Page 24-117

Significance of 3-digit readout of display group 30

1

1

1

Display zones 1 to 4

X

Lambda control
0 = inactive
1 = active

X

Lambda probe condition
0 = inactive
1 = active

X

Condition of lambda probe heating
0 = inactive
1 = active

Notes:

  • ◆ On vehicles with emission standard EU III: The lambda control of lambda probes after catalytic converters (B1-P2 and B2-P2) are not active at certain operating points without engine load, therefore the third digit of the lambda control after the catalytic converter can fluctuate between 0 and 1.
  • ◆ The first digit of the 3-digit display (heating) fluctuates between 0 and 1 at certain operating points.

Checking lambda probe learned values and lambda control

  • ‒ Connect the vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select the engine electronics control unit with "address word" 01 => Page 01-8.
    For this purpose, the engine must be running at idle speed
 
→ Indicated on display:
Rapid data transfer     HELP
Select function XX
  • ‒ Press keys 0 and 4 for the function "Introduction of basic setting" and confirm entry with Q key.

Note:

During basic setting, the solenoid valve for the activated charcoal filter (valve -N80) is closed and the air conditioner compressor is switched off.
 
→ Indicated on display:
Basic setting     
Enter display group number XXX
  • ‒ Press keys 0, 3 and 3 for "display group number 33" and confirm entry with Q key.
 
→ Indicated on display:
(1...4 = display zones)
System in basic setting 33    ⇒
    1    2    3    4
  • ‒ Check lambda control
    (display zones 1 to 4):

Display zones

1

2

3

4

Display group 33: Lambda control at idle

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

min.: -25.0 %
max.: 25.0 %

min.: 0 V
max.: 1.000 V

min.: -25.0 %
max.: 25.0 %

min.: 0 V
max.: 1.000 V

Specification

In range
-4.0...4.0 % value must fluctuate by at least
2 %

In range 0.000...1.000 volts, the voltage must fluctuate

In range
-4.0...4.0 % value must fluctuate by at least
2 %

In range 0.000...1.000 volts, the voltage must fluctuate

Note:

If the specification is not attained

If the specification is not attained, see evaluation

If the specification is not attained

If the specification is not attained, see evaluation

  • ‒ Press Ckey.
  • ‒ Press keys 0, 3 and 2 for "display group number 32" and confirm entry with Q key.
 
→ Indicated on display:
(1...4 = display zones)
System in basic setting 32    ⇒
    1    2    3    4
  • ‒ Check lambda control
    (display zones 1 to 4):

Display zones

1

2

3

4

Display group 32: Lambda probe-learned values at idle

Display

xx.x %

xx.x %

xx.x %

xx.x %

Display

Lambda learned value
bank 1, probe 1
at idle
(additive)

Lambda learned value
bank 1, probe 1
on part throttle
(multiplicative)

Lambda learned value
bank 1, probe 2
at idle
(additive)

Lambda learned value
bank 1, probe 2
on part throttle
(multiplicative)

Range

min.: -10.0 %
max.: 10.0 %

min.: -25.0 %
max.: 25.0 %

min.: -10.0 %
max.: 10.0 %

min.: -25.0 %
max.: 25.0 %

Specification

-4.0...4.0 %
can fluctuate slightly

-7.0...7.0 %
can fluctuate slightly

-4.0...4.0 %
can fluctuate slightly

-7.0...7.0 %
can fluctuate slightly

Note:

If the specification is not attained

If the specification is not attained

If the specification is not attained

If the specification is not attained

If specification is not attained in display zone 1 or display zone 3, or if the value does not fluctuate by at least 2%:

  • ‒ Check the lambda probe heating
    => Page 24-117.
  • ‒ Check lambda probe signal wiring and activation => Page 24-125
  • ‒ Test for leaks (unmetered air) in intake air system .
  • ‒ Check fuel pressure / fuel pressure regulator
    => Page 24-40
  • ‒ Fuel return line kinked or blocked.
  • ‒ Press the ⇒key.
  • ‒ Press keys 0 and 6 for the "End output" function and press the Q key to confirm entry.
  • ‒ Switch ignition off.

Interpreting display group 32

Display group 32

Display zone: 1 / 3

Possible causes of fault

Fault remedy

Lambda learned values in range
-4.0 to -10.0 %

- Oil dilution

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

Display zone: 2 / 4

- High oil consumption

Lambda learned values in range
-7.0 to -25.0 %

- Air mass meter defective

- Test air mass meter
=> Page 24-67

- Solenoid valve for activated charcoal filter stuck open

- Check solenoid valve for activated charcoal filter .

- Fuel pressure too high
- Fuel return line kinked or blocked.

- Check fuel pressure regulator
=> Page 24-40
Check fuel return line

- Injector leaking

- Check injectors => Page 24-46

Interpreting display group 32

Display group 32

Display zone: 1 / 3

Possible causes of fault

Fault remedy

Lambda learned values in range
4.0 to 10.0 %

- Unmetered air in intake area

- Check intake system for leaks and rectify unmetered air


Display zone: 2 / 4

- Fuel pressure too low

- Check fuel pressure regulator
=> Page 24-40.

Lambda learned values in range
7.0 to 25.0 %

- Lambda probe heating defective

- Check lambda probe heating
=> Page 24-117.

- Injector only opens partially or not at all

- Check injectors => Page 24-46

- Solenoid valve for activated charcoal filter stuck open

- Check solenoid valve for activated charcoal filter => Page 24-137.

Interpreting display group 33

Display group 33

Display zone: 2 / 4

Possible causes of fault

Fault remedy

approx. 0.450 V

- Open circuit in line 4 (at lambda probe) between lambda probe and control unit

- Check signal wiring and actuation => Page 24-125

- Open circuit in line 3 (at lambda probe) between lambda probe and control unit

- Lambda probe heating defective
- Lambda probe defective

- Checking lambda probe heating
=> Page 24-117
Fit a new lambda probe

Greater than 1.100 V

- Short to positive in line 4 between lambda probe and control unit

- Check lambda probe wiring for bank 1, lambda probe 1 => Page 24-126

Less than 0.100 V

- Short circuit to earth in line 4 (at lambda probe) between lambda probe and control unit
- Short circuit between lines 3 and 4

- Check lambda probe wiring for bank 2, lambda probe 1 => Page 24-130

Checking ageing of lambda probes before catalytic converter (on vehicles which conform to emission standard EU III) > < Function of lambda control