Oxygen Sensors and Oxygen Sensor Control Behind Catalytic Converter, Checking

Oxygen Sensors And Oxygen Sensor Control Behind Catalytic Converter, Checking

NOTE: The oxygen sensor before catalytic converter (bank 1, sensor 1 and bank 2, sensor 1) regulates to oxygen sensor 1. If this oxygen sensor is damaged, e.g. due to dirt or overheating, the regulation value may have shifted. Deviations from oxygen sensor 1 are detected by the oxygen sensor behind catalytic converter (bank 1, sensor 2 and bank 2, sensor 2). If it recognizes the deviations downward or upward, it influences the regulation before catalytic converter, generally increasing or decreasing it respectively.

Special tools and equipment
- VAG1526 A
- VAG1594 A
- VAG1598/31
- VAS5051 with VAS5051/1

Test requirements
- No leaks in exhaust system
- Engine coolant temperature at least 80 degrees C, display group 004, display zone 3.

Test sequence
- Connect vehicle diagnostic, testing and information system VAS5051 and select vehicle system "01 -Engine electronics" in selection. Engine must be running at idling speed.

Display on VAS5051:
- Under -1- select diagnostic function "04 - Basic setting".
1. Enter display group

Display on VAS5051:
- Enter "030" for "display group number 030" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS5051:
- Activate basic setting by pressing -A- button.
- Check specifications in display zones -2- and -4-.

NOTE:
- By increasing the engine speed the specified values are achieved more quickly.
- The "oxygen sensor status" indicates the condition of the oxygen sensor control and the oxygen sensor.

NOTE:
- The first digit of the 3-digit display (heating) fluctuates between 0 and 1.
- The oxygen sensor control for oxygen sensor behind catalytic converter (bank 1, sensor 2 and bank 2, sensor 2) is not active without engine load, i.e. the last digit of the 3-digit display is 0.

Display on VAS5051:
- Continue with test if displays have reached "110" in display zones -2- and -4- at least once.
- Press square button.

Checking oxygen sensor control behind catalytic converter

Display on VAS5051:
1. Enter display group
- Enter "038" for "display group number 038" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS5051:
- Activate basic setting by pressing -A- button.
- Check oxygen sensor voltage in display zone -2-.
- Check oxygen sensor correction value in display zone -3- and diagnosis result in display zone -4-.

Note on display zone 2:
The oxygen sensor voltage Bank 2, sensor 2 should be kept as constant as possible. Strong voltage fluctuations indicate a damaged catalytic converter.
- Press square button.

Display on VAS5051:
1. Enter display group
- Enter "038" for "display group number 038" in zone -2- and confirm entry by pressing -Q- button.

- Exit function "04 - Basic setting" by pressing square button.

Evaluation of display groups 037 and 038

Cont.
If specification in display zone 3 or 4 is not obtained:
- Perform test drive to free oxygen sensors from any possible residues and repeat test.

If specified value in display zone 3 or 4 is not obtained, even after a test drive has been performed:
- Replace relevant oxygen sensor before catalytic converter.

NOTE: If the oxygen sensor voltage is OK and after a road test the oxygen sensor correction value is still outside the specification, this indicates aging of the oxygen sensor before catalytic converter.

Checking basic voltage

- Disconnect 4-pin connector of relevant oxygen sensor behind catalytic converter,, see Fig. 6 or, see Fig. 7.

- Connect multimeter between terminals 3 and 4 to measure voltage.
- Switch ignition on.

Specified value: 0.400 to 0.500 V

- Switch ignition off.

If specified value is not obtained:
- Check oxygen sensor wiring Bank 1 or Bank 2

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

Checking oxygen sensor wiring, Bank 1 Oxygen Sensor (O2S) Behind Three Way Catalytic converter (TWC) -G130-

- Disconnect 4-pin connector, bank 1, Oxygen Sensor (O2S) behind three way catalytic converter (TWC) -G130-, see Fig. 6.
- Connect test box VAG1598/31 to wiring harness for engine control module; do not connect engine control module.

- Test for open circuit in following wiring connections.

Connector Test box VAG1598/31
terminal Socket
3 68
4 69

- Repair open circuit, if necessary.
- Check for shorts between two wires.

If no wiring malfunction is detected:
- Replace engine control module.

Checking oxygen sensor wiring, Bank 2 Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) - G131-
- Disconnect 4-pin connector, bank 2, oxygen sensor (O2S) 2 behind three way catalytic converter (TWC) -G131-, see Fig. 7.
- Connect test box VAG1598/31 to wiring harness for engine control module; do not connect engine control module. Wiring and Component Check With Test Box VAG 1598/31

- Test for open circuit in following wiring connections.

Connector Test box VAG1598/31
terminal Socket
3 10
4 11

- Repair open circuit, if necessary.
- Check for shorts between two wires.

If no wiring malfunction is detected:
- Replace engine control module.