Checking lambda control and lambda probe -G130 and -G131 downstream of catalytic converter — AUDI

AQF AQH ARU AKC AUW AVN AVP
Special tools and workshop equipment required

V.A.G 1526 A
V.A.G 1594 A
V.A.G 1598/31
V.A.G 1788/10
VAS 5051 with VAS 5051/1

or

V.A.G 1551 with V.A.G 1551/3 A

Note:

The lambda control downstream of the catalytic converter has priority over the lambda control upstream of the catalytic converter and is used as correction control.

It corrects slight mixture changes (e.g. enriches) through the lambda probe upstream of catalytic converter, by maintaining the lambda control for a certain period (dwell time) at the upper / lower point. If the time is in the positive range (e.g. 50 ms), the mixture is made richer. If it is in the negative range (e.g. -50 ms), the mixture is made leaner.

Fitting location of connector for lambda probe 2 downstream of catalytic converter:

The four-way connector for the lambda probe 2 (G130) bank 1 is under the mat on the passenger side.

The four-way connector for lambda probe 2 (G131) bank 2 is under the mat on the driver's side.

Test conditions

Perform road test and do not erase fault memory.
Coolant temperature at least 85 °C.

Test sequence

Connect the vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit 1 with "Address word" 01 => Page
01-15
.
For this purpose, the engine must be running at idling speed.

Rapid data transfer
HELP
Select function XX
Indicated on display

Enter "04" to select "Start basic setting" and confirm 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.

Initiate basic setting
Q
Enter display group number XXX
Indicated on display

Enter "034" for "display group number 034" and confirm entry with Q key.

System in basic setting 34
⇒
1
2
3
4
Indicated on display

Set engine speed to 2800...3200 rpm using engine speed controller V.A.G 1788/10.
Perform the test as soon as an exhaust gas temperature above 200°C is attained in display zone 2.

Note:

This process can take a few minutes.

Press C key.
Set engine speed to 1900...2400 rpm using engine speed controller V.A.G 1788/10.

Initiate basic setting
Q
Enter display group number XXX
Indicated on display

Enter "030" for "display group number 030" and confirm entry with Q key.

System in basic setting 30
⇒
1
2
3
4
Indicated on display

Check lambda probe status for lambda probe downstream of catalytic converter in display zones 2 and 4.

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 1, probe 2 · Lambda probe status, bank 1, probe 2 · 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 1 · 1 1 1 · 1 1 1
Note · Explanation of display => Page 24-114

Notes:

The lambda control of lambda probe downstream of catalytic converter (bank 1-probe 2 and bank 2-probe 2) is not active without engine load.
The first digit of the 3-digit display (heating) fluctuates between 0 and 1.
The third digit of the 3-digit display (lambda control) fluctuates between 0 and 1.

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

Checking lambda control downstream of catalytic converter

Carry out a road test lasting at least 10 minutes.

Initiate basic setting
Q
Enter display group number XXX
Indicated on display

Enter "037" for "display group number 037" and confirm entry with Q key.

System in basic setting 37
⇒
1
2
3
4
Indicated on display

Check lambda probe voltage in display zone 2.
Check dwell time between lambda probe 1 upstream of catalytic converter and lambda probe 2 downstream of catalytic converter in display zone 3 and diagnosis result in display zone 4.

Display zones
1 · 2 · 3 · 4
Display group 037: Diagnosis, lambda control system (Bank 1)
Display · xxx % · x.xxx volts · xxx ms · Test ON
Display · Engine load · Voltage of lambda probe downstream of catalytic converter, bank 1 · Lambda correction value between lambda probe 1 and lambda probe 1, bank 2 · Diagnosis status
Range · 15...150 % · 0...10.000 V · -1200...1200 ms · Test OFF / Test ON / Syst. OK / Syst. NOK
Specified value · 14...24 % · 0...10.000 V · -800...800 ms · Syst. OK
Note · If specified value is not attained: Evaluation, display zone 2 / =>Page . 24-112 · If specified value is not attained: Continued / =>Page . 24-113 · If "Syst. NOK" is displayed: Interrogate fault memory => Page . 24-113

Note on display zone 3:

The lambda control downstream of the catalytic converter has priority over the lambda control upstream of the catalytic converter and is used as a guidance control. It corrects slight rich / lean mixture changes in the lambda probe upstream of catalytic converter, by maintaining the lambda control upstream of catalytic converter at the upper / lower point for a certain period of time (dwell time). If the time is in the positive range (e.g. 50 ms), the mixture is made richer. If it is in the negative range (e.g. -50 ms), the mixture is made leaner.

Press the Ckey.
Press keys 0, 3 and 8 for "display group number 38" and confirm entry with Q key.

System in basic setting 38
⇒
1
2
3
4
Indicated on display:
(1...4 = display zones)

Display zones
1 · 2 · 3 · 4
Display group 038: Lambda control system diagnosis (Bank 2)
Display · xxx % · x.xxx volts · xxx ms · Test ON
Display · Engine load · Voltage of lambda probe downstream of catalytic converter, bank 2 · Lambda correction value between lambda probe 1 and lambda probe 2, bank 2 · Diagnosis status
Range · 15...150 % · 0.000...1.000 volts · -1200...1200 ms · Test OFF / Test ON / Syst. OK / Syst. NOK
Specified value · 14...24 % · 0...10.000 V · -800...800 ms · Syst. OK
Note · If specified value is not attained: Evaluation, display zone 2 / =>Page . 24-112 · If specified value is not attained: Continued / =>Page . 24-113 · If "Syst. NOK" is displayed: Interrogate fault memory => Page . 24-113

Note on display zone 3:

The lambda control downstream of the catalytic converter has priority over the lambda control upstream of the catalytic converter and is used as a guidance control. It corrects slight rich / lean mixture changes in the lambda probe upstream of catalytic converter, by maintaining the lambda control upstream of catalytic converter at the upper / lower point for a certain period of time (dwell time). If the time is in the positive range (e.g. 50 ms), the mixture is made richer. If it is in the negative range (e.g. -50 ms), the mixture is made leaner.

Evaluation of display groups 037 and 038

Display group 37/38
Display zone: 2 · Possible causes of fault · Fault remedy
approx. 0.450 V · - Open circuit in wire 4 between lambda probe and control unit · - Check signal wiring and actuation => Page 24-122
- Open circuit in wire 3 between lambda probe and control unit
- Lambda probe heating defective / - Lambda probe defective · - Check lambda probe heating / =>Page . 24-114 / Fit a new 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, lambda probe 2 (downstream of catalytic converter) => Page 24-126
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, lambda probe 2 (downstream of catalytic converter) => Page 24-130

Cont.

If specification in display zone 3 or 4 is not attained:

Check for air leak at exhaust or catalytic converter (check screw clamps and exhaust for damage)
Replace appropriate lambda probe "upstream of" catalytic converter.