Oxygen Sensor O2S Behind Three Way Catalytic Converter, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.

Special tools and workshop equipment required 

• Generic scan tool
• multimeter.
• Wiring diagram.

Test requirements

• The Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- fuse Ok.
  Fig 1: Fuses On E-Box In Engine Compartment, Left Side

  
• Oxygen Sensor O2S Behind Three Way Catalytic Converter Heater - Z29- OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, selector lever in position "P" or "N".
• A/C switched off.
• Ground (GND) connections between engine/transmission/chassis OK.
• Exhaust system between catalytic converter and cylinder head properly sealed.
• Coolant Temperature at least 80° C.

Test procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK 

Start diagnosis

-- Connect scan tool.

-- Start the engine and let it run at idle.

-- Select "Diagnostic mode 6: Check test results of components that are not continuously monitored".

-- Select "Test-ID 02: Oxygen sensor monitoring behind catalytic converter".

-- Select following Test-IDs.

-- Check the specified values at idle.

If the specified values are obtained:

-- End diagnosis and switch ignition off.

If the specified values are not obtained:

-- Remove the right vehicle floor cover -arrows-. Refer to the appropriate service manual.

Fig 2: Identifying Right Vehicle Floor Cover

Checking primary voltage

-- Disconnect the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- electrical harness connector -arrow-.

Fig 3: Disconnecting Connector For Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) G130

-- Switch the ignition on.

-- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- electrical harness connector terminals 3 to 4 for voltage.

Fig 4: Checking Component Terminals 3 To 4 For Voltage

Specified value: 0.400 to 0.500 Volts

-- Switch the ignition off.

If the specified value was not obtained:

-- Replace the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) - G130-. Refer to the appropriate service manual.

If the specified value was obtained:

Checking wiring

If the manufacturers test box is being used, perform the following step.

-- Install the test box.

If the manufacturers test box is not being used, perform the following step.

-- Remove the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate service manual.

-- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) - G130- electrical harness connector terminals to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T94 terminals for an open circuit according to the wiring diagram.

Fig 5: 4-Pin Electrical Harness Connector & Terminals

Specified value: 1.5 Ω Max.

If the specification was not obtained:

-- Check the wiring for a short circuit to Battery (+), or an open circuit.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring:

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate service manual.

-- Install the right vehicle floor cover -arrows-. Refer to the appropriate service manual.

Fig 6: Identifying Right Vehicle Floor Cover

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .