Oxygen Sensor Before Catalytic Converter, Checking

Observe all safety precautions: SAFETY PRECAUTIONS 

View clean working conditions: CLEAN WORKING CONDITIONS 

Prior to repair work, perform a preliminary check to verify the condition. Refer to PRELIMINARY CHECK .

Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.

See Appropriate Wiring Diagram Information for component locations and connector views.

Special Tools And Workshop Equipment Required 

• Multimeter
• Wiring diagram

Test Requirements 

• Fuse for Heated Oxygen Sensor (HO2S) -G39- OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Exhaust system between catalytic converter and cylinder head properly sealed.

Function Test 

-- Connect the scan tool.

-- Start engine and let it run at idle.

-- Select Diagnostic mode 6.

-- Select "Test-ID 01: Heated Oxygen Sensor". Refer to test: Monitor-ID $01: Oxygen Sensor Monitor Bank 1 - Sensor 1 Monitor-ID $01: Oxygen Sensor Monitor Bank 1 - Sensor 1 .

-- Switch ignition Off.

If The Monitor Failed: 

Checking Heater Resistance 

-- Disconnect the Heated Oxygen Sensor (HO2S) --G39-- electrical harness connector at the engine bulkhead (left side).

-- Using a multimeter, measure the resistance of the heater from terminal 3 to terminal 4 of the Heated Oxygen Sensor (HO2S) --G39-- connector.

Specified Value: 2 - 4 Ω With The Exhaust System At Room Temperature 

If The Specified Value Was Not Obtained: 

-- Replace the Heated Oxygen Sensor (HO2S) --G39--.

If The Specified Value Was Obtained: 

Checking heater voltage

-- Disconnect the Heated Oxygen Sensor (HO2S) --G39-- electrical harness connector.

-- Switch ignition On.

-- Using a multimeter, measure the voltage from terminal 4 of the Heated Oxygen Sensor (HO2S) --G39-- harness connector to ground.

Specification: Near Battery Voltage 

-- Switch ignition Off.

If Specified Value Is Not Obtained: 

-- Check for an open, short to ground or high resistance between terminal 4 of the Heated Oxygen Sensor (HO2S) --G39-- and fuse 21 (2010 Models) or fuse 4 (2011 Models) in Fuse Box B. Refer to Appropriate Wiring Diagrams for Pin/fuse locations.

-- If necessary, repair the wiring connection.

If The Specified Value Was Obtained: 

Checking HO2S voltage

-- Disconnect the Heated Oxygen Sensor (HO2S) --G39-- electrical harness connector.

-- Switch ignition On.

-- Using a multimeter, measure the voltage from terminal 3 of the Heated Oxygen Sensor (HO2S) --G39-- harness connector to ground. Refer to Appropriate Wiring Diagrams for all Pin locations.

Specification: Near 4.76 V 

-- Using a multimeter, measure the voltage from terminal 1 of the Heated Oxygen Sensor (HO2S) --G39-- harness connector to ground.

Specification: Near 2.85 V 

-- Using a multimeter, measure the voltage from terminal 5 of the Heated Oxygen Sensor (HO2S) --G39-- harness connector to ground.

Specification: Near 2.85 V 

-- Using a multimeter, measure the voltage from terminal 2 of the Heated Oxygen Sensor (HO2S) --G39-- harness connector to ground.

Specification: Near 2.50 V 

-- Using a multimeter, measure the voltage from terminal 6 of the Heated Oxygen Sensor (HO2S) --G39-- harness connector to ground.

Specification: Near 2.93 V 

-- Switch ignition Off.

If Any Of The Specified Values Were Not Obtained: 

Checking wiring 

-- Remove the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate Service Information for removal and installation procedures.

-- Using a multimeter, check the Heated Oxygen Sensor (HO2S) --G39-- electrical harness connector terminals to the Motronic Engine Control Module (ECM) -J623- electrical connector T94 for an open circuit. Refer to Appropriate Wiring Diagrams for Pin locations.

Heated Oxygen Sensor (HO2S) --G39-- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J623- electrical connector T94 terminal
Pin 1	77
Pin 2	56
Pin 3	73
Pin 5	55
Pin 6	78

Specified Resistance 1.5 Ω Max. 

If The Specification Is Not Obtained: 

-- Check the wiring for high resistance, an open or short circuit to Battery or ground.

-- If necessary, repair the wiring connection.

If No Malfunctions Are Found In Wiring And The Voltage Was Not OK: 

-- Replace the Motronic Engine Control Module (ECM) -J623-.

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 .