Oxygen Sensor Heater Behind Catalytic Converter, Checking

Special Tools And Workshop Equipment Required 

• Multimeter.
• Wiring diagram.

Test Requirements 

• The Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- fuse 21 in Fuse Panel B is OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Ignition switched off.

Test Procedure 

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

Start Diagnosis 

-- Remove the right vehicle floor cover -arrows-.

Checking internal resistance 

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

-- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- electrical harness connector terminals 1 to 2 for resistance.

Specified value: 1.0 to 20.0 Ω (at approx. 20 °C) 

If the specified value was Not obtained: 

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

If the specified value was obtained: 

Checking voltage supply

-- Turn the ignition switch ON

-- Using a multimeter, check the Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) - G130- electrical harness connector terminal 1 to engine ground.

Specified value: Battery voltage. 

If the specified value was Not obtained: 

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

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

-- If necessary, repair the faulty wiring connection.

If the specified value was obtained: 

Checking Ground (GND) activation

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 Information.

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

Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminal or test box socket
2	29

Specified value: 1.5 Ω max. 

If the specified value was Not obtained: 

-- Check the wiring for an open or high resistance.

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

-- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK: 

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate Service Information.

-- Install the 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 .