Sensors and Control Check

Heated Oxygen Sensor (HO2S) And O2S Control Before TWC, Checking

Special tools and equipment

- VAG1526A
- VAG1594A
- VAG1598/31
- VAS5051 with VAG5051/1
- or
- VAG1551 with VAG1551/3B

NOTE:
- For the specified troubleshooting procedure, it is possible, to switch oxygen sensor control off by selecting display group 99 under "Basic Setting" and switch it on again under "Read Measuring Value Block".
- After selecting display group 99 (either in "Basic Setting" or "Read Measuring Value Block"), it is possible to switch back and forth between "Basic Setting" (function 04) and "Read Measuring Value Block" (function 08) by pressing buttons 4 or 8 on the VAG1551.
- Once function 04 "Basic Setting" is exited, oxygen sensor control is automatically switched on again.
- Installation location of the oxygen sensors and harness connectors.

Test requirements:
- Road test performed and DTC memory erased.
- Coolant temperature at least 80 degree C.

Function test
- Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using "address word". Connecting VAS 5051/VAG1551 Scan Tool
- Engine must run at idle for this.

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

Indicated on display:

System in 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.

Indicated on display:

System in Basic Setting 30 ->
1 2 3 4

- Check oxygen sensor status in display field 1.

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

Display Group 030:

Significance of 3 digit indication of display group 030

Checking oxygen sensor adaptation values and control
- Press -C- button.
- Press buttons -0-, -3- and -2- to select "display group number 032" and press -Q- button to confirm input.

Indicated on display:

System in Basic Setting 32 ->
1 2 3 4

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

Display Group 032:

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

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:

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 Before and After TWC, Checking
- Check oxygen sensor before catalytic converter for aging. Oxygen Sensor Aging

Evaluation display group 032

Display Field 1/2:

Evaluation display group 033

Display Field 2:

Testing primary voltage
- Disconnect 4-pin harness connector (black) to oxygen sensor before catalytic converter; installation position.

- 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:
- 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. Wiring and Component Testing Using VAG1598/31 Test Box

- Check the 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).