Oxygen Sensors and Sensor Control After Converter, Checking

Oxygen Sensors And Oxygen Sensor Control After 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. Oxygen Sensor Heater For O2 Sensor Before Converter, Checking
- 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 degree C "Mode 1: Check measuring values "; "PID 05: Coolant temperature". Diagnostic Mode 1: Check Measured Values

Procedure
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Start engine and let run at idle.
- In diagnostic function "33 - OBD", select "Mode 5: Check output of oxygen sensor signals".

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 either the VAG1551/1552 Scan Tool (ST) or VAS5051/5052 Vehicle Diagnostic, Testing and Information System is used for checking the output of oxygen sensor signals, 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 the desired output of oxygen sensor signals according to the following table.










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







- 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 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. Test Box, Connecting For Wiring Testing







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

Harness connector Test box
Terminal Socket
3 68
4 69

- Specified value: Wire resistance max 1.5 Ohms

- Also check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinity Ohms (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. Test Box, Connecting For Wiring Testing







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

Harness connector Test box
Terminal Socket
3 10
4 11

- Specified value: Wire resistance max 1.5 Ohms

- Also check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: Infinity Ohms (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 3 - Check DTC memory. Diagnostic Mode 3: Check DTC Memory
2 - Erase DTC memory, diagnostic mode 4 - Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
3 - Generate readiness code. Readiness Code, Generating

- End diagnosis and switch ignition off.