Bosch 12008 Oxygen Sensor - Upstream

Bosch Validated Oxygen Sensor for Jeep Upstream Applications

Bosch Validated Oxygen Sensor 12008 is a specific-fit, narrow-band heated O2 sensor built for upstream use on select Jeep applications. It provides air-fuel-ratio feedback to the ECU for stable closed-loop fuel control and emissions monitoring.

Compatible With 1986-1990 Jeep Cherokee, upstream; 1986-1990 Jeep Comanche, upstream; 1987-1990 Jeep Wrangler, upstream; and 1986-1987 Jeep Wagoneer, upstream.

Key Features

• Specific-fit Bosch oxygen sensor for direct application matching
• Narrow-band heated sensor type for faster closed-loop operation
• 3-wire design with included wiring harness
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Oblong female connector with pin terminals
• Metal housing and steel finish for underbody durability
• Overall length: 12.2 in; harness length: 8.8 in

Product Details

Bosch 12008 is part of the Bosch Validated Oxygen Sensor line, which reflects Bosch’s OE development history in oxygen sensing technology. Bosch introduced early thimble-style sensors in 1976 and later advanced planar narrowband designs to improve light-off speed, lambda accuracy, and closed-loop response. This sensor uses a heated narrow-band design with ceramic sensing elements and temperature-resistant materials to maintain consistent signal output under thermal cycling and vibration. For Jeep Cherokee, Jeep Comanche, Jeep Wrangler, and Jeep Wagoneer upstream locations, Bosch 12008 supports accurate exhaust feedback for fuel management and emissions control.

This part cross-references 4778167 for the same application.

Common Issues This Sensor Can Address

• Fault codes related to oxygen sensor signal performance
• Rough idle caused by inaccurate air-fuel feedback
• Inconsistent fuel trim readings during closed-loop operation
• Elevated emissions from a worn upstream sensor
• Delayed sensor response after warm-up

Installation Notes

Verify the upstream sensor location, connector style, thread size, and harness length before installation. Use the 18 mm threaded mounting point and confirm the oblong female connector matches the vehicle harness. Inspect the exhaust bung threads and wiring routing for heat damage before installing the replacement sensor.

Quality Assurance

Bosch backs this oxygen sensor with more than five decades of OE development experience in emissions control sensing. The Bosch Validated Oxygen Sensor line is built to OE-proven standards for accuracy, durability, and consistent operation in demanding engine environments.