O2 Oxygen Sensor Upstream Downstream for Pontiac Bonneville (2004-2005) 3.8L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2004-2005 Pontiac Bonneville (G-Body)

What it Does: This matched upstream and downstream oxygen sensor kit restores closed-loop air-fuel ratio monitoring and catalytic efficiency tracking on the 2004-2005 Pontiac Bonneville L36 3.8L V6.

The Stock Pontiac Bonneville Sensor Failure

On the G-Body Bonneville equipped with the L36 3.8L V6, factory oxygen sensors endure extreme exhaust thermal cycling, carbon fouling, and oil or coolant ash contamination. Over time, internal heater circuits burn out and zirconia sensing elements lose responsiveness between 0.1V and 0.9V. When the PCM detects sluggish switching or open heater resistance, it triggers P0135, P0141, or P0171 fault codes and forces rich open-loop fueling.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light & Heater Codes: Logs P0135, P0141, or P0133 from burnt heater elements or slow sensor response.
• Fuel Trim & Idle Instability: Skewed voltage feedback forces rich fueling, causing rough idle and P0300 misfires.
• Failed Emissions & MPG Loss: Open-loop operation raises exhaust hydrocarbons and reduces highway fuel economy.

The Direct-Fit Matched Sensor Solution

Replacing both sensors as a matched set restores synchronized pre-catalyst fuel trim feedback and post-catalyst monitoring across the L36 3.8L exhaust. Each direct-fit sensor utilizes a corrosion-resistant stainless steel shell, high-temperature ceramic zirconia core, and factory-calibrated internal heater element. Pre-coated threads and OEM-style weatherpack connectors eliminate splicing, ensuring plug-and-play installation and rapid closed-loop activation from cold start.

What's Included

• 1x Upstream Oxygen Sensor
• 1x Downstream Oxygen Sensor

Technical Specifications

Compatibility

• 2004 Pontiac Bonneville 3.8L V6 (1 Upstream & 1 Downstream)
• 2005 Pontiac Bonneville 3.8L V6 (1 Upstream & 1 Downstream)

Frequently Asked Questions & Fitment Warnings

Does this fit the G-Body Bonneville?

Yes. Fits the 2004-2005 Pontiac Bonneville with the L36 3.8L V6 engine. Excludes 4.6L V8 GXP models and earlier years; verify engine before ordering.

Will this clear P0135, P0141, and P0420 codes?

Yes, for sensor-related faults. Restores voltage switching and heater resistance for P0135 and P0141; persistent P0420 codes indicate a failed catalytic converter.

Is any wiring modification required for installation?

No. Both sensors include OEM-style connectors for direct plug-and-play installation into factory G-Body exhaust bungs.

The Pontiac Precision Standard

Engineered for factory PCM accuracy, this matched sensor set keeps your L36 3.8L emissions-compliant and CEL-free. Direct-fit connectors ensure reliable fueling performance under daily thermal cycling.