Bosch 12051 Oxygen Sensor - Upstream

Bosch Oxygen Sensor for Toyota Applications

Bosch Engineered Oxygen Sensor 12051 is a specific-fit, narrow-band non-heated oxygen sensor for upstream locations on select Toyota, Chevrolet, and related applications. It provides precise air-fuel-ratio feedback to the ECU for stable combustion control and emissions monitoring.

Key Features

• Bosch Engineered Oxygen Sensor line with OE-focused design and calibration
• Part number 12051 for direct replacement applications
• Narrow-band, non-heated oxygen sensor type
• Upstream sensor position coverage for select Toyota and Chevrolet models
• Specific fit with included wiring harness
• Round connector, blade terminal, male connector and terminal design
• Flange mounting with 18 mm thread diameter and 22 mm hex size
• Metal housing built for high-temperature and vibration exposure

Product Details

Bosch 12051 is built around Bosch’s long OE development history in oxygen sensing, using a switching-type narrow-band design to report exhaust oxygen content to the engine control unit. That signal helps the ECU maintain the correct air-fuel ratio during closed-loop operation, which is important for drivability, fuel control, and emissions performance. This Bosch Engineered Oxygen Sensor is a direct-fit replacement for upstream positions on vehicles such as the Toyota Corolla, Toyota Celica, Toyota Camry, Toyota Supra, Toyota MR2, Toyota Pickup, Toyota 4Runner, Toyota Tercel, Toyota Land Cruiser, Toyota Starlet, Toyota Corona, Toyota Van, and Chevrolet Nova. This part cross-references Bosch-style OE replacement numbers such as 8942519165 and 94845519 for the same application.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Rich or lean fuel mixture readings at the ECU
• Unstable closed-loop fuel control during warm operation
• Emissions test failures tied to upstream sensor output
• Slow or inaccurate air-fuel-ratio feedback from a worn sensor

Installation Notes and Tips

Verify the vehicle’s year, make, model, and upstream sensor location before ordering. This Bosch 12051 uses a specific-fit configuration with a flange mount, 18 mm thread size, and a 17.6-inch wiring harness length. Confirm connector shape, terminal style, and harness routing against the original sensor to ensure proper installation on Toyota and Chevrolet applications.

Quality Assurance

Bosch oxygen sensors are developed from decades of OE sensor engineering and use ceramic sensing elements, controlled heater strategies where applicable, and high-temperature materials for consistent signal output under demanding exhaust conditions. Bosch 12051 is part of the Bosch Engineered Oxygen Sensor line and is built to OE-style standards for replacement use.