Oxygen Sensor (O2S) and Oxygen Sensor Control Before Three Way Catalytic Converter (TWC), Checking

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

NOTE: The Oxygen Sensor (O2S) before Three Way Catalytic Converter (TWC) (Bank 1, sensor 1) changes to Lambda 1. If this Oxygen Sensor (O2S) is damaged, e.g. through contamination or overheating, the control value can be changed. Deviations from Lambda 1 are recorded by the Oxygen Sensor (O2S) after the Three Way Catalytic Converter (TWC) (Bank 1, sensor 2). If these deviations are recognized downward or upward it influences the control before the Three Way Catalytic Converter (TWC) in such a way that it is generally raised or lowered accordingly.







Special tools and workshop equipment required
- V.A.G 1526 A Multimeter
- V.A.G 1594 A Connector test kit
- V.A.G 1598/31 Test box
- VAS 5051 Vehicle diagnostic, testing and information system
- VAS 5051/1 Adapter

Requirements
- No leaks in exhaust system
- Coolant temperature at least 80 degrees C.

Work 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.







Display on VAS 5051:
- Under -1- select diagnostic function "04 - Basic setting".







Display on VAS 5051:
1 - Enter display group
- Enter "030" for "display group number 030" in field -2- and confirm entry by pressing -Q- button.







Display on VAS 5051:
- Activate basic setting by pressing -A- button.
- Check indication in display group -2-.

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










NOTE:
- The first digit of the 3-digit display (heating) fluctuates between 0 and 1.
- The Oxygen Sensor control of the Oxygen Sensor (O2S) after Three Way Catalytic Converter (TWC) . (B1-S2) is inactive without engine load.







Display on VAS 5051:
- Only continue test if display in display field -2- has reached "110" at least once.
- Press <- button.

Oxygen Sensor control behind Three Way Catalytic Converter (TWC), checking







Display on VAS 5051:
1 - Enter display group
- Enter "037" for "display group number 037" in field -2- and confirm entry by pressing -Q- button.







Display on VAS 5051:
- Activate basic setting by pressing -A- button.
- Check Oxygen Sensor (O2S) voltage in display field -2-.
- Check Oxygen Sensor (O2S) correction value in display field-3- and diagnosis result in display field -4-.







Note on display field 2:
- The Oxygen Sensor (O2S) voltage bank 1, sensor 2 should be kept as constant as possible. Strong voltage fluctuations indicate a damaged Three Way Catalytic Converter (TWC).

Evaluating display group 037







(cont.)
If specification in display field 3 or 4 is not obtained:
- Perform test drive to free Oxygen Sensor (O2S) from any possible residues and repeat test.

If specified value in display field 3 or 4 is not obtained, even after a test drive has been performed:
- Replace Oxygen Sensor (O2S) before Three Way Catalytic Converter (TWC).

NOTE: If the Oxygen Sensor (O2S) 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 the Three Way Catalytic Converter (TWC).

Checking basic voltage







- Disconnect 4-pin connector -2- (brown) to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC).







NOTE: To gain access to the connector, remove coolant expansion tank bolt (arrow) and move expansion tank to side. Fuel hoses remain connected.







- 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 obtained:
- Replace Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-.

If specified value is not obtained:







- Disconnect 4-pin connector -2- (brown) to Heated Oxygen Sensor (HO2S) -G39-.







NOTE: To gain access to the connector, remove coolant expansion tank bolt (arrow) and move expansion tank to side. Fuel hoses remain connected.

- Connect test box V.A.G 1598/31 to wiring harness for Engine Control Module (ECM); do not connect Engine Control Module (ECM).







- Test for open circuit in following wiring connections.

Connector Test box V.A.G 1598/31
terminal Socket
3 68
4 69

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

If wiring is OK:
- Replace Engine Control Module (ECM)