O2 Oxygen Sensor Upstream Downstream for Chevrolet Impala (2004-2005) 3.8L

Direct-Fit O2 Oxygen Sensor Kit for 2004-2005 Chevrolet Impala (W-Body)

What it Does: Restores closed-loop fuel metering and catalyst monitoring on 2004-2005 Chevrolet Impala (W-Body) 3.8L L36/L67 models.

The Stock Chevrolet Impala Oxygen Sensor Failure

Over high mileage, OEM oxygen sensors on the W-Body Impala suffer thermal fatigue, internal heater circuit burnout, and zirconia poisoning from oil ash or carbon fouling. When the upstream sensor on the 3.8L L36 or supercharged L67 turns sluggish, voltage switching slows and corrupts PCM fuel trims. Downstream element degradation then prevents accurate catalyst oxygen-storage monitoring, triggering persistent P0131, P0135, P0141, and P0420 fault codes.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light: Triggers P0134, P0135/P0141 (heater circuit), or P0171/P0172 fuel trim codes.
• Poor MPG & Rich Exhaust: Sluggish switching forces rich open-loop fueling and fouls plugs.
• Rough Idle & Emissions Failure: Unstable fuel trims cause surging and failed readiness monitors.

The Direct-Fit Heated Zirconia Oxygen Sensor Solution

This matched replacement kit pairs upstream (234-4646) and downstream (234-4647) direct-fit sensors engineered to restore factory PCM response on naturally aspirated and supercharged 3.8L exhaust manifolds. Each unit features a fast-light-off ceramic heater and a laser-welded stainless protective shield built to resist moisture shock and exhaust heat soak. Factory-length leads with OEM-style weatherpack connectors plug directly into the W-Body chassis harness with zero cutting or splicing.

What's Included

• 1 Upstream Oxygen Sensor (234-4646)
• 1 Downstream Oxygen Sensor (234-4647)

Technical Specifications

Compatibility

• 2004-2005 Chevrolet Impala 3.8L (Naturally Aspirated L36) — Upstream & Downstream
• 2004-2005 Chevrolet Impala 3.8L (Supercharged L67) — Upstream & Downstream

Frequently Asked Questions & Fitment Warnings

Does this fit the W-Body Impala?

Yes. Fits 2004-2005 Chevrolet Impala (W-Body) with the 3.8L L36/L67 V6. Confirm 3.8L engine before ordering; excludes 3.4L V6 models.

Will this clear P0135 or P0420 codes?

Yes, if sensor-induced. Replacing 234-4646 and 234-4647 resolves heater and switching DTCs; persistent P0420 requires catalyst inspection.

Are the electrical connectors plug-and-play?

Yes. Sensors include OEM plugs; apply anti-seize only to threads before installation.

The Chevrolet Precision Standard

Replacing both sensors as a matched set restores fuel trim accuracy and emissions readiness on your W-Body Impala. Built for exhaust heat durability, this 3.8L kit ensures CEL-free operation.