With Manufacturer's Scan Tool

Oxygen Sensor (O2S) And Oxygen Sensor Control Before Catalytic Converter, Checking

Special tools and equipment







- V.A.G 1526 A Multimeter
- V.A.G 1594 A Connector test kit
- V.A.G 1598/31 Test box
- VAS 5051 with VAS 5051/1

Test requirements:
- No leaks in exhaust system
- Coolant temperature at least 80 degree C.

Test sequence
- Connect vehicle diagnostic, testing and information system VAS 5051 and select vehicle system "01 -Engine electronics" in selection. Engine must be run at idle speed. Connecting VAS 5051/VAG 1551 Scan Tool (ST)

Display on VAS 5051:







- Under -1- select diagnostic function "04 - Basic setting".

Display on VAS 5051:







1 Enter display group max. input value 255
- Enter "030" for "display group number 030" in field -2- and confirm entry by pressing -Q- button.

Display on VAS 5051:







- Check specification in display field -1-.

NOTE:
- By increasing engine speed specified values are achieved more quickly.
- The "Oxygen Sensor status" indicates condition of Oxygen Sensor control and Oxygen Sensor (O2S).

Display Group 030:

NOTE: The first digit of the 3-digit display (heating) fluctuates between 0 and 1.

Display on VAS 5051:







- Only continue test if display in display field -1- has reached "111" at least once.

Checking Oxygen Sensor (O2S) adaptation values and Oxygen Sensor (O2S) control
- Press the uparrow button twice to change "display group number 032".
- Check indication in display groups -1-and -2-.







Display on VAS 5051:







- Press the uparrow button to change "display group number 033".
- Check indication in display groups -1-and -2-.







Continued
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 (O2S) Heating -Z19- Before TWC, Checking
- Check oxygen sensor before catalytic converter for aging. Oxygen Sensor (O2S) Aging (HO2S Before TWC), Checking













Testing primary voltage
- Disconnect 6-pin harness connector (black) to Heated Oxygen Sensor (HO2S) -G39-.







- Connect multimeter between terminal 1 and 5 for voltage measurement.
- Switch ignition on.
- Specification: 0.400 to 0.500 V
- Switch ignition off.

If specified value is not obtained:
- Test oxygen sensor wires.

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

Testing oxygen sensor wires
- Disconnect 4-pin harness connector (black) to oxygen sensor before catalytic converter.
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Electrical Testing Using VAG1598/31 Test Box







- Check the following wire connections for open circuit.

Harness connector VAG1598/31 test box
Terminal Socket
1 70
2 71
5 51
6 52

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

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