1. Buick Envision O2 Sensor

Factory Part Number (OE NO):
Upstream(Front) Oxygen Sensor part No.: 12658134 (2.0T LSY engine)
Downstream(Rear) Oxygen Sensor part No.: 12658135
Defender Oxygen Sensor Fault Codes & Symptom Signs
P0131: Front Oxygen Sensor Circuit Voltage Too Low (Insufficient Fuel Supply from Fuel Pump or Wiring Aging)
P0171: Excessively Thin Mixture (Dirty MAF Sensor or Vacuum Leak)
What causes & How to repair
Frequent starting and stopping under congested city road conditions leads to carbon buildup and delayed sensor response; intermittent insufficient fuel supply from the fuel pump after long distance highway driving.
How much oxygen sensor cost to replace ?
Genuine sensor: 250-400 (labor cost 80-150)
Sub-factory parts (e.g. USGM): 150-250

2.Buick LaCrosse O2 Sensor

Genuine part number (OE NO):
Upstream(Front) Oxygen Sensor part No.: 12645789 (3.6L V6 engine)
Downstream(Rear) Oxygen Sensor part No.: 12645790
Defender Oxygen Sensor Fault Codes & Symptom Signs
P0420: Catalytic converter inefficient (Rear Oxygen Sensor Poisoning or 3-way Catalytic converter failure)
P2195: Front Oxygen Sensor Signal Fixed High Voltage (Poor Fuel Quality or Clogged Injector)
What causes & How to repair
Long-term low-speed driving of commercial vehicles leads to carbon deposits on the sensor; sulfide accelerates sensor poisoning after using ethanol gasoline.
How much oxygen sensor cost to replace ?
Original sensor: 300-450 (labor cost 100-200)

3.Buick Enclave O2 Sensor

Genuine part number (OE NO):
Upstream(Front) Oxygen Sensor part No.: 12658136 (3.6L V6 engine)
Downstream(Rear) Oxygen Sensor part No.: 12658137
Defender Oxygen Sensor Fault Codes & Symptom Signs
P0030: Oxygen Sensor Heating Circuit Fault (Shorted wiring harness or abnormal ECU power supply)
P2271: Rear Oxygen Sensor Signal Sticky Low Voltage (High Fuel Sulfur Content)
What causes & How to repair
Overheating of the sensor due to high engine load when towing a motorhome; delayed response of the heating circuit due to low temperatures in cold areas.
How much oxygen sensor cost to replace ?
OEM sensor: 350-500 (labor 150-250)

4.Buick Regal O2 Sensor

Genuine part number (OE NO):
Upstream(Front) Oxygen Sensor part No.: 12658132 (2.0T LTG engine)
Downstream(Rear) Oxygen Sensor part No.: 12658133
Defender Oxygen Sensor Fault Codes & Symptom Signs
P0134: Front Oxygen Sensor No Signal (Plug Oxidized or Circuit Disconnected)
P2096: Rear Oxygen Sensor Signal Too Dilute (Exhaust System Leak)
What causes & How to repair
Sports driving mode with rich mixture, accelerating carbon buildup; Modified exhaust system causing sensor signal interference
How much oxygen sensor cost to replace ?
OEM sensor: 280-420 (labor cost 80-120)

5.Buick Encore O2 Sensor

Genuine part number (OE NO):
Upstream(Front) Oxygen Sensor part No.: 12658130 (1.4T engine)
Defender Oxygen Sensor Fault Codes & Symptom Signs
P0130: Oxygen Sensor Faulty Signals (Poisoned or Broken Sensor)
P0172: Excessive mixture (Fuel Pressure Sensor Fault)
What causes & How to repair
Short city commutes cause delayed sensor response at low temperatures; excessive use of fuel additives causes signal drift.
How much oxygen sensor cost to replace ?
Genuine sensor: 200-300 (labor cost 50-100)

6.Buick Encore GX O2 Sensor

Original part number (OE NO):
Upstream(Front) Oxygen Sensor part No.: 12658131 (1.3T engine)
Defender Oxygen Sensor Fault Codes & Symptom Signs
P2270: Rear Oxygen Sensor Signal Sticky (Heater Circuit Fault)
P2297: Fuel Pressure & Oxygen Signal Conflict (High Pressure Fuel Pump Fault)
What causes & How to repair
Sensor overheating after rapid acceleration in turbocharged models; sensor poisoning due to fuel dilution in small-displacement engines
How much oxygen sensor cost to replace ?
OEM sensor: 220-350 (labor cost 80-120)
General maintenance recommendations
Troubleshooting Priority:
Wiring check: 40% of oxygen sensor failure caused by the aging of the wiring harness or plug oxidation, priority to use a multimeter to detect the power supply and grounding (reference voltage 0.45V ± 0.1V)
Carbon cleaning: use ferric chloride solution to soak the sensor probe (cost 30-50), can restore 50% of the sensor performance
Parts selection strategy:
Genuine parts: best fit, recommended 4S store replacement (including ECU programming)
Sub-factory parts: USGM, GMF and other brands cost-effective, need to verify compatibility through the VIN
Cost optimization program:
Purchase the sensor by yourself and then entrust the third-party repair, you can save 30%-50% of labor costs
Data Source and Expansion Suggestion
The above information is compiled from GM Technical Bulletins, USGM/GMF brand manuals and repair cost statistics. For verification of part number fitment, we recommend checking the GM EPC system (GM Parts Now). For real-time price fluctuations, please refer to RepairPal or local repair platforms.

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