Oxygen Sensor Before Catalytic Converter, Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements 

• The Heated Oxygen Sensor (HO2S) -G39- fuse OK.
• The Oxygen Sensor (O2S) Heater -Z19- before catalytic converter 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.
• Coolant Temperature at least 80.3 °C.
• Ignition switched OFF.

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 "Monitor-ID $01: Oxygen sensor monitoring before catalytic converter".

-- Select "Test-ID $83: Dynamic test".

-- Check the specified values at idle.

Dynamic test		Specified value
		min.	max.
Normal operation		0.150	-
Reduced threshold upon suspicion of malfunction in catalytic converter		0.399	-

If the specified values were obtained:

-- Switch the ignition OFF. Fault is not active at this time. Check for poor connections, loose terminals and perform a harness check.

If the specified values are Not obtained:

Checking primary voltage 

-- Disconnect the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector -1-.

-- Turn the ignition ON.

-- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal 1 for voltage.

Specified value: 2.45 to 2.99 Volts

-- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal 2 for voltage

Specified value: 2.25 to 2.79 Volts

-- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal 3 for voltage.

Specified value: 3.10 to 3.70 Volts

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

Specified value: Battery voltage

-- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal 5 for voltage.

Specified value: 2.69 to 2.99 Volts

-- Using a multimeter connected to Ground, check the Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminal 6 for voltage.

Specified value: 2.79 to 3.20 Volts

If all of the specified values were obtained:

-- Replace the Heated Oxygen Sensor (HO2S) -G39-. Refer to the Repair information.

If any of the specified values were Not obtained:

Checking wiring 

-- 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 terminals to the Engine Control Module (ECM) -J623- electrical harness connector T94 terminals for an open circuit.

Heated Oxygen Sensor (HO2S) -G39- electrical harness connector terminals:	Engine Control Module (ECM) -J623- electrical connector T94 terminals:
1	78
2	79
3	73
4	fuse (Refer to Wiring Diagrams for number)
5	56
6	57

Specified value: 1.5 Ω Max.

If the specified value was Not obtained:

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

-- 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 Not OK:

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

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 .