Oxygen Sensor 4-Pack, OE Replacement 234-4668 SG1857

A 4-Piece Oxygen Sensor Set, OE Replacement

This is a set of 4 direct-fit, threaded-in oxygen sensors, cross-referenced to part numbers 234-4668 and SG1857. If your check engine light is on with an oxygen sensor code stored, you've noticed a drop in fuel economy, or your vehicle's exhaust smells noticeably richer than usual, a worn oxygen sensor is one of the most common and most affordable things to check first.

Why Oxygen Sensors Matter So Much to How an Engine Runs

An oxygen sensor measures how much unburned oxygen is left in the exhaust after combustion, and the engine computer uses that reading in real time to fine-tune how much fuel it injects on every single cycle. Because that feedback loop runs continuously while the engine is running, a sensor that's reading slowly, inaccurately, or not at all forces the computer to rely on default fuel settings that are rarely as efficient as the constantly adjusted readings a healthy sensor provides, which is why a single failing sensor can measurably affect both fuel economy and emissions.

Key Features

• Cross-referenced to part numbers 234-4668 and SG1857
• Set of 4 sensors for a complete replacement
• 4-wire, threaded-in direct-fit design
• Manufactured to OE replacement specifications

Specifications

• Type: 4-wire oxygen sensor
• Mounting style: Threaded-in
• Quantity: 4 sensors per set
• Recommended use: OE replacement
• Condition: New

Compatibility

These sensors are cross-referenced to part numbers 234-4668 and SG1857. Because oxygen sensor part numbers are matched to specific engine and exhaust configurations rather than to a single universal design, it's worth confirming these numbers against your vehicle's original sensor or its OEM part number before ordering, or contacting us with your VIN if you're unsure.

Signs Your Oxygen Sensors Need Replacing

A failing oxygen sensor typically triggers a check engine light with a stored code referencing the sensor's specific location, along with symptoms like reduced fuel economy, a rough or uneven idle, a noticeable sulfur or rotten-egg smell from the exhaust, or a failed emissions test. Because most vehicles use multiple oxygen sensors positioned before and after the catalytic converter, a single sensor going bad can also cause the computer to misjudge how well the catalytic converter itself is working, sometimes triggering a second, unrelated-seeming code.

Why Sensors Are Often Replaced as a Full Set

Oxygen sensors on a given vehicle are typically installed at the same time on the assembly line and see the same heat cycling, exhaust exposure, and mileage over the life of the vehicle, which means they tend to wear out on a similar timeline even if one triggers a code before the others. Replacing all four together rather than one at a time avoids a scenario where a fresh sensor is giving the computer accurate readings while an aging one nearby has already started to drift, which can make diagnosing future issues more straightforward as well.

Installation Notes

Replacing these sensors means locating each sensor along the exhaust system, disconnecting its electrical connector, unscrewing it with an oxygen sensor socket or wrench, and threading in the new sensor before reconnecting the harness. Because oxygen sensor threads are sometimes coated with anti-seize compound from the factory to ease future removal, applying a small amount of anti-seize to the new sensor's threads before installation is generally recommended unless the sensor's packaging says otherwise.

Ordering Information

This oxygen sensor set is in stock and ships ready to install. Our Shipping Information page covers current timelines, and our Warranty and Returns pages explain what to do if anything isn't right on arrival. Not sure these match your specific vehicle? Our Request a Part page is the fastest way to confirm before you order.

Related Parts

This oxygen sensor set is listed in our Sensors & Electronics collection, where you'll find other engine management components for your vehicle.