Sensor and Control Check

Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter, Checking

Special Tools and Equipment

- VAG1526A
- VAG1594A
- VAG1598/31
- VAG1788/10 RPM adjuster
- VAS5051 with VAG5051/1
or
- VAG1551 with VAG1551/3B

NOTE:
- The oxygen sensor control behind catalytic converter overrules the oxygen sensor control before catalytic converter. It serves as a corrective control.

- It corrects slight changes in the mixture (i.e. enrichment) via the oxygen sensor before catalytic converter by holding oxygen sensor control before catalytic converter at its higher or lower point for a specific time (dwell time). If this time is in the positive range (i.e. 50 ms), mixture is shifted in the -enrich- direction. If it is in the negative range (i.e. -50 ms), mixture is shifted in the -lean- direction.

Test Requirements:
- Road test performed and DTC memory erased.
- Coolant temperature at least 80 °C See Display group 4, display field 3

Test Sequence
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word" 01. Refer to "Scan Tool Testing/Scan Tool Connecting And Initial Checks", Testing and Inspection

Engine must run at idle for this.

When indicated on display:

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -4- to select "Initiate basic setting" and press -Q- button to confirm input.

NOTE: During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off

When indicated on display:

Basic Setting Q
Input display group number XXX

- Press buttons -0-, -3- and -4- to select "display group number 034" and press -Q- button to confirm input.

When indicated on display:

System in Basic Setting 34 ->
1 2 3 4

- Use VAG1788/10 RPM adjuster to adjust engine speed to between 2800 and 3200 RPM.
- Continue test as soon as display field 2 indicates an exhaust temperature of more than 380 °C

NOTE: This process can take a few minutes.

- Press -C- button.
- Let engine continue to idle

When indicated on display:

Basic Setting Q
Input display group number XXX

- Press buttons -0-, -3- and -0- to select "display group number 030" and press -Q- button to confirm input.

When indicated on display:

System in Basic Setting 30 ->
1 2 3 4

- Check oxygen sensor status for oxygen sensor behind catalytic converter in display fields 2 and 4.

NOTE: "Oxygen sensor status" indicates status of oxygen sensor control and oxygen sensors.

Significance of 3 digit indication of display group 030

- Press -C- button.

When indicated on display:

Basic Setting Q
Input display group number XXX

- Press buttons -0-, -4- and -3- to select "display group number 043" and press -Q- button to confirm input.

When indicated on display:

System in Basic Setting 43 ->
1 2 3 4

- Check specified value in display field 4 after indication "Test ON" appears:

If specified value B1-S2 OK" is obtained:
- Press -C- button.
- Press buttons -0-, -4- and -4- to select "display group number 044" and press -Q- button to confirm input.

When indicated on display:

System in Basic Setting 44 ->
1 2 3 4

- Check specified value in display field 4 after indication "Test ON" appears:

If specified value B2-S2 OK" is obtained:
- Press -C- button.

Checking oxygen sensor control behind catalytic converter
- Perform a test drive of approx. 10 minutes.

WARNING!
Observe safety precautions to reduce the risk of accidents during road test.

- Let engine continue to run at idle.

When indicated on display:

Basic Setting Q
Input display group number XXX

- Press buttons -0-, -3- and -7- to select "display group number 037" and press -Q- button to confirm input

When indicated on display:

System in Basic Setting 37 ->
1 2 3 4

- Check oxygen sensor voltage in display field 2.
- Check dwell time between oxygen sensor 1 before catalytic converter and oxygen sensor 2 behind catalytic converter in display field 3 and diagnostic result in display field 4.

- Press -C- button.
- Press buttons -0-, -3- and -8- to select "display group number 038" and press -Q- button to confirm input.

When indicated on display:

System in Basic Setting 38 ->
1 2 3 4

- Check specified value in display field 4.

NOTE: The test in display group 038 is activated simultaneously with the test in display group 037 Therefore the test result is indicated immediately after display group 038 is selected.

Evaluation of display group 037 and 038

If specified value in display group 037 and 038 display field 3 or 4 is not obtained:
- Search for leaking air at exhaust system or catalytic converter (check screw clamps and exhaust system for damage).
- Check if possibly the oxygen sensors behind catalytic converter of cylinder bank 1 and 2 have been switched, in case of extremely different values (e.g. +500 ms, -500 ms) of display fields 3 (oxygen sensor correction value) in the measuring value blocks 037 and 038.

If none of the listed causes applies:
- Replace respective oxygen sensor -before- catalytic converter

Checking Primary Voltage
- Disconnect 4-pin harness connector leading to respective oxygen sensor.

- Connect multimeter between terminal 3 and 4 for voltage measurement.
- Switch ignition on.
- Specification: 0.400 to 0.500 V

- Switch ignition off.

If specified value is not obtained:
- Check oxygen sensor wires, Bank 1, bank 2.

If specified value is obtained:
- Replace appropriate oxygen sensor behind catalytic converter.

Testing Oxygen Sensor Wires
- Disconnect green 4-pin harness connector 1 to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-.
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Refer to "Scan Tool Testing/Wire And Component Test Using VAG1598/31 Test Box", Testing and Inspection

- Check the following wire connections for open circuit.

Harness connector Terminal VAG1598/31 test box Socket
3 68
4 69

- Repair open circuit if necessary.
- Check wires to each other for short circuit.

Harness connector Terminal VAG1598/31 test box Socket
4 68

- Check shielded wire for short circuit to sensor wires.

Harness connector Terminal VAG1598/31 test box Socket
3 32
4 32

If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).

Check oxygen sensor wires for Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-.
- Disconnect brown 4-pin harness connector 2 to Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-.
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Refer to "Scan Tool Testing/Wire And Component Test Using VAG1598/31 Test Box", Testing and Inspection

- Check the following wire connections for open circuit.

Harness connector Terminal VAG1598/31 test box Socket
3 10
4 11

- Repair open circuit if necessary.
- Check wires to each other for short circuit.

Harness connector Terminal VAG1598/31 test box Socket
4 10