Oxygen Sensor 2 After Catalytic Converter - GX8-, Checking

General Description

The Oxygen Sensor 2 After Catalytic Converter -GX8- is positioned downstream of the primary catalytic converter and it supplies the Engine/Motor Control Module -J623- with a voltage signal (nonlinear) indicating a "rich" or a "lean" condition is present. If the primary catalytic converter is supersaturated with oxygen (indicating a lean mixture is present), the Oxygen Sensor 2 After Catalytic Converter -GX8- will send the Engine/Motor Control Module -J623- a nonlinear signal indicating the lean mixture condition. The mixture is then enriched with fuel until the oxygen has been "displaced" from the catalytic converter. This new condition, in turn, is registered by the Oxygen Sensor 2 After Catalytic Converter -GX8- as a nonlinear signal indicating the rich mixture condition. The mixture is then leaned out by the Engine/Motor Control Module -J623-. If the nonlinear signal is received again, the mixture will again be enriched. The frequency, or period, during which the mixture is enriched or leaned out is variable, being dependent on the gas flow rate (engine load) at that moment.

Note the Oxygen Sensor 2 After Catalytic Converter -GX8- is also known as the Oxygen Sensor 2 After Catalytic Converter -G131-.

The Oxygen Sensor 2 After Catalytic Converter -GX8- contains the following components:

Oxygen Sensor 2 After Catalytic Converter -G131-.
Heater For Oxygen Sensor 2 After Catalytic Converter -Z30-.

The Oxygen Sensor 2 After Catalytic Converter -GX8- components cannot be serviced separately, and they must be serviced as a unit.

Special tools and workshop equipment required

Multimeter.
Wiring Diagram.
Scan Tool.

Test requirements

Fuses OK.
Battery voltage OK.
Switch OFF all electrical and electronic accessories.
Vehicles with automatic transmission, ensure the selector lever position is in "P".
Vehicles with manual transmission, ensure the shifter lever position is in "N" with the parking brake applied.
Observe all safety precautions: SAFETY PRECAUTIONS .
View clean working conditions: CLEAN WORKING CONDITIONS .

Test Procedure

Step	Procedure	Result / Action to Take
1	PERFORM: Preliminary Check to verify the customers complaint. Refer to Oxygen Sensor Preliminary Tests in PRELIMINARY CHECK . -- Was Complaint verified?	-- YES: GO TO: Step 2. -- NO: GATHER more information from customer about the complaint.
2	IGNITION: OFF. DISCONNECT: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector. CHECK: Oxygen Sensor 2 After Catalytic Converter -GX8- component connector terminals 1 to 2 for resistance. SPECIFIED VALUE: 2 - 4 Ω (+/- 0.5 Ω @ 25° C). -- Was Value obtained?	-- YES: GO TO: Step 3. -- NO: REPLACE: Oxygen Sensor 2 After Catalytic Converter -GX8-. Refer to appropriate Service Information. GO TO: Step 6.
3	IGNITION: ON. CHECK: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector terminal 1 to ground for voltage. IGNITION: OFF. SPECIFIED VALUE: Battery voltage. -- Was Value obtained?	-- YES: GO TO: Step 4. -- NO: PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 6.
4	RECONNECT: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector. CONNECT: Scan Tool. START: Engine and let Idle. Perform the function test located in diagnostic mode 06. Refer to appropriate Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions, DIAGNOSTIC MODES 01 - 0A . IGNITION: OFF. SPECIFIED VALUE: Mode 6 Pass. -- Were Values obtained?	-- YES: FAULT: Is intermittent. PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 6. -- NO: GO TO: Step 5.
5	DISCONNECT: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector. REMOVE: Engine/Motor Control Module -J623-. Refer to appropriate Service Information. CHECK: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector terminal 2 to the Engine/Motor Control Module -J623- harness connector T56c / 55 for resistance. CHECK: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector terminal 3 to the Engine/Motor Control Module -J623- harness connector T56c / 22 for resistance. CHECK: Oxygen Sensor 2 After Catalytic Converter -GX8- harness connector terminal 4 to the Engine/Motor Control Module -J623- harness connector T56c / 18 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: REPLACE: Oxygen Sensor 2 After Catalytic Converter -GX8-. Refer to appropriate Service Information. GO TO: Step 6. -- NO: PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 6.
6	Final Procedure Perform a road test to verify repair. -- Does the original DTC return?	-- YES: CHECK: Engine/Motor Control Module -J623- harness connector for any damaged, pushed-out pins. REPAIR: As necessary. If all electrical connections are OK: REPLACE: Engine/Motor Control Module -J623-. Refer to appropriate Service Information. Clear the DTC's. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY . Repair is complete. Generate Readiness Code. Refer to READINESS CODE . Return vehicle to Customer. -- NO: Perform the diagnostic procedure for any DTC's. If no DTC's return, the repair is complete. Return vehicle to customer.