Oxygen Sensor After Catalyst Checking
Oxygen sensor control and Oxygen Sensors (02S) -G130- and -G131- behind Three Way Catalytic Converter (TWC), checking
Special tools and equipment
- VAG 1526 A
- VAG 1594 A
- VAG 1598/31
- VAG 1788/10
- VAS 5051 with VAS 5051/1
- or
- V.A.G 1551 with V.A.G 1551/3 A
NOTE:
- The oxygen sensor control after the catalytic converter is superior to the oxygen sensor control before the catalytic converter and is used as correction control.
- It corrects slight mixture changes (e.g. enriches) through the oxygen sensor before the catalytic converter, by maintaining the oxygen sensor 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.
Test conditions
- Perform road test and do not erase DTC memory.
- Coolant temperature at least 85 degrees C.
Test sequence
- Connect vehicle diagnostic, testing and information system VAS 5051 or VAG 1551 Scan Tool and select engine electronics control module 1 with "Address word" 01. For this purpose, engine must be running at idle speed.
Connecting VAS 5051 Scan Tool
[1][2]Scan Tool Connecting and Initial Checks
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 EVAP canister purge regulator valve -N80- is closed and the air conditioner compressor is switched off.
Indicated on display
Initiate basic setting Q
Enter display group number XXX
- Enter "034" for "display group number 034" and confirm entry with Q key.
Display readout
System in basic setting 34 ->
1 2 3 4
- Set engine speed to 2800...3200 rpm using engine speed controller VAG 1788/10.
Perform the test as soon as an exhaust gas temperature above 250 degrees C is attained in display zone 2.
NOTE: This process can take a few minutes.
- Press C key.
- Set engine speed to 1800...2400 RPM using engine speed controller VAG 1788/10.
Indicated on display
Initiate basic setting Q
Enter display group number XXX
- Enter "030" for "display group number 030" and confirm entry with Q key.
Indicated on display
System in basic setting 30 ->
1 2 3 4
- Check oxygen sensor status for oxygen sensor after catalytic converter in display zones 2 and 4.
NOTE: The "oxygen sensor status" indicates the condition of the oxygen sensor control and the oxygen sensors.
Display Group 030:
Meaning of 3 digit readout of display group 30
Meaning of 3 digit readout of display group 30:
- Press C button.
Indicated on display
Initiate basic setting Q
Enter display group number XXX
- Enter "043" for "display group number 043" and confirm entry with Q key.
Indicated on display
System in basic setting 43 ->
1 2 3 4
- Check specified value in display zone 4.
Display Group 043:
If specified value "B1-S2 OK" is obtained:
- Press C button.
- Enter "044" for "display group number 044" and confirm entry with Q key.
Display Group 044:
If specified value "B2-S2 OK" is obtained:
- Press C button.
Checking oxygen sensor control after catalytic converter
- Perform a road test lasting at least 10 minutes.
Indicated on display
Initiate basic setting Q
Enter display group number XXX
- Enter "037" for "display group number 037" and confirm entry with Q key.
Display readout
System in basic setting 37 ->
1 2 3 4
- Check oxygen sensor voltage in display zone 2.
- Check dwell time between oxygen sensor 1 before catalytic converter and oxygen sensor 2 after catalytic converter in display zone 3 and diagnosis result in display zone 4.
Display Group 037:
- Press Ckey.
- Press keys 0, 3 and 8 for "display group number 38" and confirm entry with Q key.
Indicated on display: (1...4 display zones)
System in basic setting 38 ->
1 2 3 4
Display Group 038:
Evaluation of display groups 037 and 038
Display Group 37/38:
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 oxygen sensor "before" catalytic converter.