Oxygen Sensor Before Catalytic Converter, Checking

Oxygen Sensor And Oxygen Sensor Control Before Catalytic Converter, Checking

Special tools and equipment
- VAG1526A
- VAG1594A
- VAG1598/31
- VAS5051 with VAG5051/1
- or
- VAG1551 with VAG1551/3A

Test requirements:
- Exhaust system free of leaks.
- Coolant Temperature at least 80 °C

Test sequence
- Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Engine must run at idle. [1][2]Scan Tool Connecting and Initial Checks

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.

When indicated on display

Basic Setting Q
Enter display group number XXX

- Press buttons -0-, -3- and -0- to select "display group number 030" and press -Q- button to confirm input
- Check specified value in display field 1.

NOTE:
- Increase engine speed to obtain specified values faster.
- "Oxygen sensor status" indicates status of oxygen sensor control and oxygen sensors.

Display Group 030:

- Do not start test until indication in display field 1 has reached "111" at least once.

Checking oxygen sensor adaptation values and control
- Press -C- button.

When indicated on display

Basic Setting Q
Enter display group number XXX

- Press buttons -0-, -3- and -2- to select "display group number 032" and press -Q- button to confirm input.

When indicated on display

System in basic setting 32 ->
1 2 3 4

- Check oxygen sensor values in display fields 1 and 2:

Display Group 036:

- Press -C- button.

When indicated on display

Basic Setting Q
Enter display group number XXX

- Press buttons -0-, -3- and -3- to select "display group number 033" and press -Q- button to confirm input.

When indicated on display

System in basic setting 33 ->
1 2 3 4

- Check oxygen sensor control in display fields 1 and 2.

Display Group 033:

Continuation
If specified value in display field 1 is not obtained or if value does not fluctuate at least 2 %:
- Road test vehicle in order to free oxygen sensor of possible residue and repeat test.

If specified value in display field 1 is not obtained even after road test or if value does not fluctuate at least 2 %:
- Check primary voltage.
- Check oxygen sensor heating. Oxygen Sensor Control Behind Catalytic Converter Checking Oxygen Sensor Control After Catalytic Converter, Checking
- Check oxygen sensor before catalytic converter for aging.

Display group 032

Display Field 1/2 - Part 1:

Display Field 1/2 - Part 2:

Evaluation display group 033

Display Field 2:

Checking primary voltage

- 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 wiring.

If specified value is obtained:
- Replace Heated Oxygen Sensor (HO2S) -G39-.

Checking oxygen sensor wires

- Disconnect 4-pin harness connector -2- (black) to Heated Oxygen Sensor (HO2S) -G39- before catalytic converter.

NOTE: Coolant reservoir screws must be removed and coolant reservoir must be placed to side in order to access the harness connector. The coolant hoses can remain connected.

- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM), do not connect ECM. [1][2]Scan Tool Connecting and Initial Checks

- Check following wire connections for open circuit.

Harness connector VAG1598/31 test box
Terminal Socket
3 51
4 70

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

If wire connection is OK:
- Replace Engine Control Module (ECM).