O2 Oxygen Sensor Upstream Downstream for Chevrolet Avalanche (2002-2006) 5.3L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2002-2006 Chevrolet Avalanche (GMT800)

What it Does: This 4-piece upstream and downstream oxygen sensor kit restores closed-loop air-fuel ratio monitoring and catalyst efficiency tracking on the GMT800 2002-2006 Chevrolet Avalanche 1500 equipped with the LM7 5.3L V8.

The Stock Chevrolet Avalanche Sensor Failure

Factory zirconia sensors on the GMT800 platform suffer thermal fatigue from continuous 1,400°F+ exhaust exposure on the LM7 5.3L V8. Over time, platinum electrode contamination, oil-ash fouling, and heater-circuit burnout slow voltage switching between rich and lean states. Sluggish upstream response skews PCM fuel trims, while degraded downstream sensors trigger P0135, P0155, or P0420/P0430 faults across Bank 1 and Bank 2.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light & DTCs: Stored fault codes such as P0135, P0141, P0155, or P0171/P0174 from open heater circuits and slow sensor switching.
• Fuel Trim Drift: Delayed voltage transitions force open-loop enrichment, causing rough idle, black exhaust soot, and sluggish throttle response.
• Failed Emissions & MPG Loss: Inaccurate exhaust oxygen readings cut highway fuel economy and prevent OBD-II readiness monitors from setting.

The Direct-Fit 4-Sensor Oxygen Kit Solution

Replacing all four sensors simultaneously as a matched set balances Bank 1 and Bank 2 fuel-trim feedback across the LM7 5.3L V8 exhaust stream. Each unit features a laser-welded stainless housing, ceramic zirconia sensing element, and PTFE-sealed breather cable to resist moisture and underbody salt corrosion. Pre-terminated OEM connectors ensure plug-and-play fitment matching interchange numbers 234-4012 and 250-24012 with no wire splicing.

What's Included

• 2 Upstream Oxygen Sensors
• 2 Downstream Oxygen Sensors

Technical Specifications

Compatibility

• 2002-2006 Chevrolet Avalanche 1500 5.3L (GMT800) — 2 Upstream & 2 Downstream Positions
• Excludes 6.0L and 8.1L engines (different catalytic converter and sensor layout)
• Excludes 2007-2013 Chevrolet Avalanche 5.3L models

Frequently Asked Questions & Fitment Warnings

Does this fit the GMT800 Avalanche?

Yes. This is a direct fit for the 2002-2006 Chevrolet Avalanche 1500 equipped with the LM7 5.3L V8 engine. Excludes 6.0L, 8.1L, and 2007-2013 5.3L Avalanche models; confirm engine before ordering.

Will this clear P0135, P0155, or P0420/P0430 codes?

Yes, when caused by faulty sensors. Restoring heater resistance and switching speed clears P0135, P0155, and false P0420/P0430 codes after a drive cycle, provided the catalytic converter substrate is intact.

Are the connectors plug-and-play for installation?

Yes. All four sensors feature factory-style connectors that plug straight into the OEM harness with no cutting or splicing required; torque threaded sensors to factory spec.

The Chevrolet Heavy-Duty Standard

Built for the towing loads and high underbody exhaust temperatures of the GMT800 Avalanche 1500, this matched 4-sensor kit restores crisp closed-loop fuel metering. Reliable voltage feedback protects your catalytic converters and keeps the LM7 5.3L V8 operating efficiently under load.