GM GENUINE PARTS Heated Oxygen (O2) Sensor AFS138 (19178961) — Direct-Fit OE Heated Replacement for GM Trucks

GM Genuine Parts AFS138 (19178961) is a heated oxygen (O2) sensor engineered to replace the original factory unit, helping the engine control module maintain correct air/fuel balance.

This GM-backed heated oxygen sensor monitors exhaust oxygen levels so the vehicle’s engine control module (ECM) can trim fuel delivery and keep combustion close to the target air/fuel ratio. Built to General Motors OE specifications, the AFS138 is designed for direct fit and reliable operation in compatible Chevrolet, GMC, and Cadillac models. It’s a GM-recommended replacement for the original factory component and carries the durability and validation expected from a genuine OEM part.

How does this sensor affect engine performance and emissions?

The heated oxygen sensor provides real-time feedback on exhaust gas oxygen percentage, enabling the ECM to adjust fuel injection for cleaner combustion and stable engine operation. While it does not change engine design, a properly functioning O2 sensor helps maintain fuel efficiency and supports emission control systems.

• Measures oxygen content in exhaust to inform fuel trims
• Supports catalytic converter efficiency by maintaining correct air/fuel ratio
• Reduces risk of rough idling or increased fuel consumption when working correctly

What vehicles and fitments does the AFS138 serve?

This specific GM Genuine Parts AFS138 (19178961) matches the original equipment specifications for a range of GM trucks and SUVs from late 1990s to early 2000s model years. Always verify the OEM part number and vehicle application before purchase to ensure compatibility.

• Chevrolet: Avalanche 1500 (2002), Tahoe, Suburban 1500, Silverado 1500 (1999–2002), Silverado 2500 (1999–2000)
• GMC: Yukon/Yukon XL 1500 (2002), Sierra 1500 (1999–2002), Sierra 2500 (1999–2000)
• Cadillac: Escalade (2002)
• Connector type: Female; designed for direct replacement of factory-installed sensor

Why choose a GM Genuine Parts sensor over an aftermarket option?

GM Genuine Parts are engineered or validated by General Motors to match the original factory component in fit, form, and function. Choosing an OEM sensor reduces the chance of fitment issues, electrical incompatibility, or reduced durability compared with unknown aftermarket units.

• Manufactured to GM OE specifications for consistent performance
• Backed by GM validation and part-number traceability
• Connector and harness compatibility for easier installation

How will I know when the oxygen sensor needs replacement?

Symptoms that suggest an oxygen sensor is failing include a persistent check engine light, reduced fuel economy, or erratic engine idle. Diagnostic trouble codes (DTCs) from an OBD-II scan often indicate the affected sensor bank or circuit, helping you confirm the need for replacement.

• Common signs: check engine light, poor fuel mileage, rough idling
• Confirm with OBD-II codes for O2 sensor or fuel trim abnormalities
• Replace with the GM part number for an exact fit and connector match

Who is this for: The GM Genuine Parts AFS138 (19178961) heated oxygen sensor is intended for owners and technicians working on compatible Chevrolet, GMC, and Cadillac trucks and SUVs from the listed model years who want a direct OE replacement. If you need a sensor that matches factory specifications, uses the original connector style, and is validated by General Motors for fit and performance, this GM Genuine Parts unit is built for that purpose.