Checking lambda control and lambda probes -G39 and -G108 upstream of catalytic converter — AUDI

BRV
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

Notes:

For defined fault finding, lambda control can be deactivated under "Basic setting" and activated again under "Reading measured value block" on selecting display group 99.

Test requirements:

No leaks in exhaust system
Coolant temperature at least 80 °C=>Display group 004, display zone 3

Test sequence

Connect up vehicle diagnostic, testing and information system VAS 5051=>Page
01-7
and select vehicle system "01 - Engine electronics" from list. Engine must be idling.

Indicated on VAS 5051:

From list -1- select diagnostic function "04 - Basic setting".

Indicated on VAS 5051:

1 -
Enter display group

Use keypad -2- to enter "030" for "Display group number 030" and confirm by touching Q key.

Indicated on VAS 5051:

Check display in zones -1- and -3-.

Notes:

Specifications are obtained faster by increasing engine speed.
"Lambda probe status" indicates status of lambda control and lambda probes.

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 X X · X X X X
Significance · Lambda probe status bank 1, probe 1 · Lambda probe status bank 1, probe 2 · Lambda probe status bank 2, probe 1 · Lambda probe status bank 2, probe 2
Operating range · 0 = off / 1 = on · 0 = off / 1 = on · 0 = off / 1 = on · 0 = off / 1 = on
Specification · X X 1 1 1 · X 1 1 0 · X X 1 1 1 · X 1 1 0
Note · Explanatory notes on display => Page 24-177

Note:

Only the last three positions on the right in the five-position display (in zones 1 and 3) or the four-position display (in zones 2 and 4) are relevant.

Explanatory notes on 3-position display in display group 30

Note:

Only the last three positions on the right in the five-position display (in zones 1 and 3) or the four-position display (in zones 2 and 4) are relevant.

1 · 1 · 1 · Display zones 1 to 4
X · Lambda control / 0 = not active / 1 = active
X · Lambda probe condition / 0 = not active / 1 = active
X · Status of lambda probe heating / 0 = not active / 1 = active

Note:

First zone of 3-position display (heating) fluctuates between 0 and 1.

Indicated on VAS 5051:

Do not continue with test until display in zones -1- and -3- has reached "00111" at least once.
Touch ◂ key.

Checking lambda probe learned values and control

Indicated on VAS 5051:

1 -
Enter display group

Use keypad -2- to enter "033" for "Display group number 033" and confirm by touching Q key.
Check display in zones -1- to -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 V · xx.x % · x.xxx V
Significance · Lambda control / bank 1 · Lambda probe voltage, bank 1 · Lambda control / bank 2 · Lambda probe voltage, bank 2
Operating range · min.: -25.0 % / max.: 25.0 % · min.: 0.000 V / max.: 1.000 V · min.: -25.0 % / max.: 25.0 % · min.: 0.000 V / max.: 1.000 V
Specification · In range / -10.0...10.0 % value must fluctuate by at least / 2 % · In range 0.000...1.000 V voltage must fluctuate · In range / -10.0...10.0 % value must fluctuate by at least / 2 % · In range 0.000...1.000 V voltage must fluctuate
Note · If reading does not match specification / => Page 24-153 · If reading does not match specification, refer to evaluation / =>Page 24-156 · If reading does not match specification / =>Page 24-153 · If reading does not match specification, refer to evaluation / =>Page 24-156

Touch ◂ key.

Indicated on VAS 5051:

1 -
Enter display group

Use keypad -2- to enter "032" for "Display group number 032" and confirm by touching Q key.

Indicated on VAS 5051:

Activate basic setting by touching key -A-.
Check display in 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 %
Significance · Lambda learned value / bank 1, probe 1 / at idle / (additive) · Lambda learned value / bank 1, probe 1 / at part throttle / (multiplicative) · Lambda learned value / bank 2, probe 1 / at idle / (additive) · Lambda learned value / bank 2, probe 1 / at part throttle / (multiplicative)
Operating range · min.: -25.0 % / max.: 25.0 % · min.: -25.0 % / max.: 25.0 % · min.: -25.0 % / max.: 25.0 % · min.: -25.0 % / max.: 25.0 %
Specification · -7.0...7.0 % / May fluctuate slightly · -7.0...7.0 % / May fluctuate slightly · -7.0...7.0 % / May fluctuate slightly · -7.0...7.0 % / May fluctuate slightly
Note · If reading does not match specification / =>Page 24-155 · If reading does not match specification / =>Page 24-155 · If reading does not match specification / =>Page 24-155 · If reading does not match specification / =>Page 24-155

Terminate function "04 - Basic setting" by touching ◂ key.

If reading in display zone 1 or 3 (display group 33) does not match specification or if value does not fluctuate by at least 2 %:

Perform test drive to remove any residue from lambda probes and repeat test.

If reading in display zone 1 or 3 still does not match specification following test drive or if value does not fluctuate by at least 2 %:

Check lambda probe heating
=>Page
24-177
.
Check lambda probe signal wire and actuation => Page
24-182
.
Check intake system for leaks and eliminate unmetered air
=> Page
24-124
.
Check fuel pressure regulator => Page
24-59
.
Fuel return pipe kinked or clogged

Evaluation of display group 32

Display group: 32
Display zone: 1 / 3 · Possible cause of trouble · Fault remedy
Lambda learned values in range: / -7.0 to -25.0 % · - Oil dilution · - Change oil or drive for long distance at good speed
Display zone: 2 / 4 · - High oil consumption
Lambda learned values in range: / -7.0 to -25.0 % · - Air mass meter defective · - Check air mass meter / => Page 24-104
- Activated charcoal filter system solenoid valve 1 stuck open · - Check activated charcoal filter system solenoid valve 1 => Page 24-196
- Fuel pressure too high / - Fuel return pipe kinked or clogged · - Check fuel pressure regulator / => Page 24-59 / Check fuel return pipe
- Injector leaking · - Check injectors => Page 24-66

Evaluation of display group 32

Display group: 32
Display zone: 1 / 3 · Possible cause of trouble · Fault remedy
Lambda learned values in range: / 7.0 to 25.0 % · - Unmetered air in intake system · - Check intake system for leaks and eliminate unmetered air / => Page 24-124
/ Display zone: 2 / 4 · - Fuel pressure too low · - Check fuel pressure regulator / => Page 24-59
Lambda learned values in range: / 7.0 to 25.0 % · - Lambda probe heating defective · - Check lambda probe heating / => Page 24-177
- Injector not opening or only partially · - Check injectors => Page 24-66
- Activated charcoal filter system solenoid valve 1 stuck open · - Check activated charcoal filter system solenoid valve 1 => Page 24-196

Evaluation of display group 33

Display group: 33
Display zone: 2 / 4 · Possible cause of trouble · Fault remedy
approx. 0.450 V · - Open circuit in wire 4 between lambda probe and control unit · - Check signal wire and actuation / => Page 24-182
- Open circuit in wire 3 between lambda probe and control unit
- Lambda probe heating defective / - Lambda probe defective · - Check lambda probe heating / => Page 24-177 / Replace lambda probe
Greater than 1.100 V · - Short to positive in wire 4 between lambda probe and control unit · - Check lambda probe wiring, bank 1 probe 1 => Page 24-183
Less than 0.100 V · - Short to earth in wire 4 between lambda probe and control unit / - Short circuit between wires 3 and 4 · - Check lambda probe wiring, bank 2 probe 1 => Page 24-188