Bosch 18125 Oxygen Sensor

Bosch Oxygen Sensor for OE-Style Emissions Control

Bosch Part Number 18125 is a narrow-band heated oxygen sensor built for precise air-fuel ratio feedback to the ECU. It supports stable combustion control and emissions management across changing engine loads, temperatures, and driving conditions.

Compatible With Ram 2500, Ram 3500, Dodge Charger, Chrysler 300, Mercedes-Benz CLS550, and other listed applications, this Bosch Engineered Oxygen Sensor line reflects Bosch’s OE development history and focus on fast closed-loop response. The Bosch 18125 uses a threaded metal housing, 4-wire configuration, and included wiring harness for a direct replacement setup.

Key Features

• Part Number: 18125
• Bosch Engineered Oxygen Sensor standard replacement
• Narrow-band heated oxygen sensor for air-fuel ratio monitoring
• Specific fit application with 4-wire, pin-terminal design
• Rectangle female connector with included wiring harness
• Threaded mounting, 18 mm thread size, 22 mm hex size
• Metal housing built for high-temperature and vibration exposure
• Wiring harness length: 13.6 in; overall length: 16.9 in

Detailed Description

Bosch developed its oxygen sensor technology from early thimble-style designs to later planar narrowband sensors that respond faster and reach operating temperature more quickly. This Bosch 18125 oxygen sensor uses advanced ceramic sensing elements and controlled heater operation to deliver consistent signal output for closed-loop fuel control. It is a direct-fit, specific application sensor for vehicles that require a narrow-band heated O2 sensor with a 4-pin female connector.

This part cross-references Mopar 56028994AA and 68144248AD for the same application. It is also listed for select Ram 2500 and Ram 3500 applications, along with Chrysler 300 and Dodge Charger fitments, making it a practical OE-style replacement for emissions service.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel mixture feedback to the ECU
• Delayed closed-loop operation after startup
• Rough combustion control caused by aging sensor response
• Emissions test failures tied to sensor signal degradation

Installation Notes and Tips

• Verify the exact position before ordering; this part is listed for upstream left, upstream right, upstream, downstream left, and downstream right applications depending on vehicle.
• Confirm the 18 mm thread size and threaded mounting location match the original sensor.
• Inspect the connector shape, terminal count, and harness routing before installation.
• Use the vehicle’s service information for torque and connector routing specifications.
• For fitment examples, this part is listed for 2023-2024 Ram 1500 Classic, upstream left; 2022-2023 Chrysler 300, downstream right; and 2021-2023 Dodge Charger, downstream right.

Quality Assurance

Bosch backs this oxygen sensor with more than five decades of OE development experience. The Bosch Engineered Oxygen Sensor line is built to OE-proven standards for accurate signal output, durable construction, and dependable emissions control performance.