Oxygen Sensor Bank 2 Sensor 1 Heater Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements 

• Fuse -- -SB11- 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 air filter.

-- Disconnect the Heated Oxygen Sensor (HO2S) 2 -G108- electrical harness connector -1-.

Checking internal resistance 

-- Using a multimeter, check the Heated Oxygen Sensor (HO2S) 2 -G108- terminals 3 to 4 for resistance.

Specified value: 1.5 to 10.0 Ω (at approx. 20°C)

If the specification was Not obtained:

-- Replace the Heated Oxygen Sensor (HO2S) 2 -G108-.

If the specification was obtained:

Checking voltage supply 

-- Using a multimeter, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal 4 to ground for voltage.

-- Crank the engine.

Specified value: Battery voltage.

-- Switch the engine Off.

If the specification was Not obtained:

-- Check the Heated Oxygen Sensor (HO2S) 2 -G108- electrical harness connector terminal 4 to the Motronic Engine Control Module (ECM) Power Supply Relay -J271- socket 2/87 for an open circuit, high resistance, a short circuit to each other, Battery (+) or Ground.

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

-- If necessary, repair the faulty wiring connection.

If the specification was obtained:

Checking Ground 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 Engine Control Module (ECM) -J623-. Refer to the Repair Information.

-- Using a multimeter, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector to the Engine Control Module (ECM) -J623- electrical harness connector T121 for resistance.

Heated Oxygen Sensor (HO2S) 2 -G108- electrical harness connector terminal	Engine Control Module (ECM) -J623- electrical connector T121 terminal or test box socket
3	4

Specified value: 1.5 Ω max.

If the specification was Not obtained:

-- Check the wiring for an open circuit, high resistance, a short circuit to each other, Battery (+) and Ground.

-- 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 and the voltage supply was OK:

-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .

-- Perform a road test to verify repair.

If the DTC does not return:

Generate readiness code. Refer to READINESS CODE .

If the DTC returns, no malfunction is found in the wiring and the voltage supply was OK:

-- Replace the Engine Control Module (ECM) -J623-. Refer to the Repair Information.

-- Assembly is performed in the reverse of the removal.

Final procedures 

After 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 .