Oxygen Sensors and Oxygen Sensor Regulation Behind Catalytic Converter, Checking

Oxygen Sensors And Oxygen Sensor Regulation Behind Catalytic Converter, Checking

NOTE: When servicing terminals 3 and 4 in harness connector of oxygen sensors, use only gold-plated terminals.

Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram

Test requirements







- Fuses in E-box (plenum chamber, left) must be OK
- Motronic Engine Control Module (ECM) Power Supply Relay 2 -J670- -position A1- must be OK, check
- Battery voltage must be at least 11.5 volts.
- All electrical consumers such as, lights and rear window defroster must be switched off.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in -P-.
- If vehicle is equipped with an A/C system, it must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- Exhaust system must be properly sealed between catalytic converter and cylinder head.
- Coolant temperature must be at least 80 degrees C, Diagnostic mode 1: Check measured values; PID 5, Coolant temperature. Diagnostic Mode 01 - Read Current System Data
- Oxygen sensor heater for oxygen sensor behind catalytic converter must be OK, check. Oxygen Sensor Heater For Oxygen Sensors Behind Three Way Catalytic Converter (TWC), Checking

Function test
- Select the lambda test results and check whether the specified values are being reached, Diagnostic mode 5: Check output of oxygen sensor signals. Diagnostic Mode 05 - Read Oxygen Sensor Monitoring Test Results
- End diagnosis and switch ignition off.

If specified values are not obtained:
- Test oxygen sensor wires according to wiring diagram.

Checking oxygen sensor wires
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test







- Disconnect 4-pin harness connector to the respective oxygen sensor:
- Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-, bank 1, 4-pin harness connector 2-,
- Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-, bank 2, 4-pin harness connector -3-.







- Check wires between test box and 4-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Wire resistance: max. 1.5 ohms







- Also check wires for short circuit to B+ or Ground (GND).

Specified value: infinity ohm

If no malfunctions are found in wires:
- Replace respective oxygen sensor:
- Heated Oxygen Sensor (HO2S) -G130- bank 1
- Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Readiness Code