Heated Oxygen Sensor (HO2S) and Oxygen Sensor Control Behind Three Way Catalytic Converter (TWC), Checking

Checking Heated Oxygen Sensor (HO2S) And Oxygen Sensor Control Behind Three Way Catalytic Converter (TWC)

NOTE: The oxygen sensor before catalytic converter (bank 1, sensor 1) regulates to Lambda 1. If this oxygen sensor is damaged, e.g. due to soiling or overheating, the regulation value may have shifted. Deviations from Lambda 1 are detected by the oxygen sensor behind catalytic converter (bank 1, 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
- VAG1526A or Fluke 83 Multimeter
- VAG1594A Connector test kit
- VAG1598/31 Test box
- VAG1788/10 RPM adjuster
- VAS5051 Vehicle diagnosis, testing and information system with VAS5051/1 Adapter

Requirements
- Exhaust system free of leaks.
- Coolant Temperature at least 80 degrees C.

Work sequence
- Connect VAS5051 tester, Vehicle Diagnostic, Testing and Information System VAS 5051, Connecting and Selecting Functions and select vehicle system "01 - Engine electronics". Engine must run at idle.







Display on VAS5051:
- In selection -1-, click on diagnostic function "04 - Basic Setting".







Display on VAS5051:
1 - Enter display group. Max. input value = 255
- Select function "030" in button field -2- for "display group number 030" and press Q button to confirm input.







Display on VAS5051:
- Check specified value in display field 2.

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

















Display on VAS5051:
Do not continue test until indication in display field 2 has reached "110" at least once.

Checking oxygen sensor control behind catalytic converter
- Use VAG1788/10 RPM adjuster to adjust engine speed to 2000 RPM.
- Click on <- button







Display on VAS5051:
1 - Enter display group. Max. input value = 255

- Select function "037" in button field -2- for "display group number 037" and press -Q- button to confirm input.







Display on VAS5051:
- Check oxygen sensor voltage in display field 2.
- Check oxygen sensor correction value in display field 3 and diagnostic result in display field 4.







Evaluation display group 037







Continuation
If specified value in display field 3 and 4 is not obtained:
- Road test vehicle in order to free oxygen sensor of possible residue and repeat test.

If specified value in display field 3 and 4 is not obtained, even after road test:
- Replace Heated Oxygen Sensor (HO2S) -G39-.

NOTE: If oxygen sensor voltage is OK and oxygen sensor correction value is still above 0.02 ms, even after a road test, this suggests aging of an oxygen sensor before catalytic converter.

Checking primary voltage







- Remove protective cover -2- (arrows).
- Disconnect 4-pin harness connector (brown) to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-.







- Connect multimeter between terminal 3 and 4 for voltage measurement
- Switch ignition on.
- Specified value: 0.400 ... 0.500 V
- Switch ignition off.

If specified value is not obtained:
- Check oxygen sensor wiring.

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

Checking oxygen sensor wires
- Disconnect 4-pin harness connector (brown) to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-.
- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM) but do not connect ECM. Scan Tool Testing and Procedures







- Check following wiring connections for open circuit.

Harness connector VAG1598/31 test box
Terminal Socket
3 68
4 69

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

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