Oxygen Sensor and Oxygen Sensor Control Behind Catalytic Converter, Checking

Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter, Checking

NOTE: The oxygen sensor before catalytic converter (bank 1, sensor 1 or bank 2, 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 or bank 2, sensor 2). If it recognizes the deviations downward or upward, it influences the regulation before catalytic converter, generally increasing or decreasing it respectively.







Recommended special tools and equipment
- VAG1526A multimeter
- VAG1594A connector test kit
- VAG1598/31 test box

Test requirements:
- Fuses for engine electronics OK
- Ground (GND) connections at engine and transmission OK
- Oxygen sensor heater OK; check.
- Exhaust system free of leaks.
- Parking brake engaged.
- Vehicles with automatic transmission: Selector lever in position "P" or "N".
- Electrical consumers switched off (radiator fan must NOT run during test).
- A/C switched off.
- Coolant temperature at least 80 degrees C; "PID 05: Coolant temperature". Diagnostic Mode 01 - Read Current System Data

Work procedure
- Connect diagnostic tester. VAS 5051, Connecting and Select Functions
- Start engine and let run at idle.
- In diagnostic function "33 - OBD", select "Mode 5: Check Lambda test results".

NOTE:
- Bank 1 = cylinder bank 1 in direction of travel, right; Bank 2 = cylinder bank 2 in direction of travel, left.
- When selecting the diagnostic mode, the entry is always performed in "Bank 1 sensor 1".
- If the Vehicle Diagnostic, Testing and Information System VAS 5051 or the Vehicle Diagnostic and Information System VAS 5052 is used for checking the lambda test results, the respective oxygen sensor can be selected by pressing button 1, 2, 5 and 6:
- Button 1 = Bank 1 sensor 1,
- Button 2 = Bank 1 sensor 2,
- Button 5 = Bank 2 sensor 1,
- Button 6 = Bank 2 sensor 2.
- Select desired output of oxygen sensor signals according to the following table.

Test-ID Diagnostic text Specified value
min. max.
07: Minimum voltage at sensor for test cycle
- Bank 1, sensor 2 0.000 V 0.625 V
- Bank 2, sensor 2 0.000 V 0.625 V
08: Maximum voltage at sensor for test cycle
- Bank 1, sensor 2 0.625 V 1,000 V
- Bank 2, sensor 2 0.625 V 1,000 V







- Check values of output for oxygen sensor signals.
- *) V = Voltage in Volts (oxygen sensor signal)
- **) t = Time in seconds

If specified values are not obtained:
- Road test vehicle in order to free oxygen sensors of possible residue and repeat test.

If specified values are not obtained again:

Checking primary voltage







- Disconnect electrical 4-pin harness connector -3- from Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- and Oxygen Sensor (O2S) Heater 1 (behind Three Way Catalytic Converter (TWC)) -Z29- (bank 1, sensor 2).







- Disconnect electrical 4-pin harness connector -1- from Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131- and Oxygen Sensor (O2S) Heater 2 (behind Three Way Catalytic Converter (TWC)) -Z30- (bank 2, sensor 2).







NOTE: To reach the harness connectors, the left cover in engine compartment must be removed, the line to Engine Coolant Level (ECL) Warning Switch at bottom on reservoir must be disconnected, bolt (arrow) of coolant reservoir must be removed and set it aside. Coolant hoses -1- to -3- remain connected.







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

If specified value is not obtained:
- Check oxygen sensor wires Bank 1 and Bank 2.

If specified value is obtained:
- Replace respective oxygen sensor behind catalytic converter.

Check oxygen sensor wires for Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- (bank 1, sensor 2)
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected.







- Check the following wire connections for open circuit according to wiring diagram:

Harness connector Terminal Test box Socket
3 68
4 69

- Specified value: Wire resistance max 1.5 Ohms
- Check wires for short circuit to each other as well as to B+ and Ground (GND).

- Specified value: Infinity ohm (no continuity)

- If necessary, repair wire connection.

If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).

Check oxygen sensor wires for Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G131- (bank 2, sensor 2)
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected.






- Check the following wire connections for open circuit according to wiring diagram:

Harness connector Terminal Test box Socket
3 10
4 11

- Specified value: Wire resistance max 1.5 Ohms

- Check wires for short circuit to each other as well as to B+ and Ground (GND).

- Specified value: Infinity ohm (no continuity)

- If necessary, repair wire connection.

If no malfunctions are found in wires:
- Replace Engine Control Module (ECM).

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If DTC memory was erased, generate readiness code.

- End diagnosis and switch ignition off.