A-Premium O2 Oxygen Sensor Downstream 4-Wire Heated — Direct-Fit for Chevy, GMC, Buick, Hummer (400mm)

The A-Premium O2 oxygen sensor is a direct-fit downstream, 4-wire heated replacement designed to restore accurate exhaust oxygen readings for compatible GM and related vehicles.

This premium aftermarket sensor replaces worn or failing downstream (post-catalytic) oxygen sensors on a range of Chevrolet, GMC, Buick, Hummer, Pontiac, Saab and Saturn models. Built with a heated sensing element and a threaded mounting style, the unit matches OE electrical connections and dimensions (4 wires, 400 mm overall length) so it installs without modification. Use the reference part numbers to confirm compatibility with your vehicle.

Which vehicles will this A-Premium O2 sensor fit?

This oxygen sensor is specified as a downstream (post-cat) unit and fits many GM-family models across the late 2000s and early 2010s. Match the engine, model year and bank/sensor position (B1S2 or B2S2) listed for each vehicle to ensure correct fitment before ordering.

• Buick: Enclave 2008 3.6L, LaCrosse 2010 2.4L, Lucerne 2009–2011 3.9L, Rainier 2007 4.2L
• Chevrolet: Captiva Sport, Colorado, Equinox, Malibu, Orlando, Trailblazer (years/engines listed in product details)
• GMC/Hummer/Pontiac/Saturn/Saab/Isuzu: Multiple models including Acadia, Canyon, Envoy, Terrain, H3/H3T, G6, Solstice, Aura, Outlook, Sky, Vue, 9-7x, Ascender, i-290, i-370

How does the sensor's specification affect performance and installation?

The heated 4-wire design speeds warm-up so the engine control module receives accurate oxygen data sooner after startup. Threaded mounting and a male connector mirror factory parts, simplifying installation and reducing the need for adaptors or rewiring.

• Heated element: faster operating temperature for reliable readings
• 4 wires: separate heater circuit plus signal/ground for stable data
• 400 mm length: engineered to reach factory harness routing without strain
• Threaded mount: installs into original bung like OEM sensors

What reference numbers and part details should I check before buying?

Compare the reference numbers and physical specs to the part you are replacing. The listing includes multiple OEM cross-references to help identify the correct downstream sensor for your vehicle.

• Reference numbers: 12599204, 12604538, 12617907, 12597947, 12618010, 12618012, 250-24708, 25024708
• Connector gender: male — matches factory harness receptacle
• Packaging: single sensor per box for one-to-one replacement
• Mounting type: threaded to fit factory exhaust bungs

Who is this replacement sensor for?

This A-Premium downstream oxygen sensor is intended for DIY mechanics, independent repair shops and fleet technicians replacing a failing post-catalytic O2 sensor on compatible GM-based vehicles. It’s suitable when diagnostics report a downstream sensor fault, when you need a reliable one-to-one OE-style replacement, or when restoring correct emissions monitoring after exhaust repairs. Always verify vehicle year, engine size and bank/sensor position against the fitment list and reference numbers to ensure proper selection.